PATENT DOCUMENT

Publication Number: US-10919326-B2
Application Number: US-201916457212-A
Country: US
Kind Code: B2

Title: Controlled ablation and surface modification for marking an electronic device

Abstract:
An article having a laser-formed marking is disclosed. The article includes a coating defining an exterior surface of the article and the marking extends through the coating. The marking comprises a recessed marking feature which provides a color or other visual attribute to the marking.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a device component comprising:
 a metal substrate; 
 a coating layer formed along at least a front surface of the metal substrate and comprising:
 a first layer disposed over the at least the front surface of the metal substrate and comprising a polymer binder and inorganic pigment particles dispersed within the polymer binder; and 
 a second layer disposed over the first layer and comprising a transparent polymer defining at least a portion of an exterior surface of the electronic device; and 
 
 a marking formed along the exterior surface and comprising a laser-formed relief feature having:
 at least one recess wall partially defining a recess extending through the first layer and the second layer; and 
 a recessed marking feature defining a bottom of the recess and visually distinct from an adjacent portion of the coating layer. 
 
 
 
     
     
       2. The electronic device of  claim 1 , wherein:
 the recessed marking feature includes an oxide layer formed over the metal substrate; and 
 a color of the recessed marking feature is due, at least in part, to a thickness of the oxide layer. 
 
     
     
       3. The electronic device of  claim 1 , wherein:
 the laser-formed relief feature includes:
 a groove extending into the metal substrate and defining a pair of groove walls; 
 a first metal oxide layer extending along a first wall of the pair of groove walls and having a first thickness defining, in part, a first color; and 
 a second metal oxide layer formed along a second wall of the pair of groove walls, having a second thickness different from the first thickness, and defining, in part, a second color. 
 
 
     
     
       4. The electronic device of  claim 3 , wherein an apparent color of the recessed marking feature is due to a combined effect of the first color and the second color. 
     
     
       5. The electronic device of  claim 3 , wherein:
 the groove is v-shaped; and 
 an angle defined between the first wall and the second wall of the pair of groove walls is from about 60 degrees to about 120 degrees. 
 
     
     
       6. The electronic device of  claim 1 , wherein the laser-formed relief feature further comprises a depression formed into the metal substrate. 
     
     
       7. The electronic device of  claim 6 , wherein a depth of the depression is less than 500 μm. 
     
     
       8. The electronic device of  claim 1 , wherein:
 the recessed marking feature comprises a texture along the front surface of the metal substrate; and 
 the texture defines, at least in part, a reflectance of the recessed marking feature. 
 
     
     
       9. An electronic device comprising:
 a device component comprising:
 a metal material; 
 a multilayer coating formed over a surface of the metal material and comprising:
 a first layer disposed over the surface of the metal material and comprising a binder and pigment particles dispersed within the binder; and 
 a second layer disposed over the first layer and comprising a transparent polymer; and 
 
 a marking formed into the multilayer coating and comprising:
 a first recessed marking feature along the surface of the metal material and visually distinct from the multilayer coating; and 
 a laser-formed relief feature at least partially surrounding the first recessed marking feature and having:
 a recess wall partially defining a recess extending through the first layer and the second layer of the multilayer coating; and 
 a second recessed marking feature visually distinct from an adjacent portion of the multilayer coating and defining, in part, a bottom of the recess. 
 
 
 
 
     
     
       10. The electronic device of  claim 9 , wherein:
 the first recessed marking feature further comprises a metal oxide layer formed along the surface of the metal material; and 
 the first recessed marking feature has a marking color defined, at least in part, by a thickness of the metal oxide layer. 
 
     
     
       11. The electronic device of  claim 9 , wherein the first recessed marking feature further comprises:
 a first metal oxide layer along a first region of the surface of the metal material and having a first thickness; 
 a second metal oxide layer along a second region of the surface of the metal material and having a second thickness; and 
 the first recessed marking feature has a first marking color defined, at least in part, by the first thickness and a second marking color defined, at least in part, by the second thickness. 
 
     
     
       12. The electronic device of  claim 9 , wherein the second recessed marking feature comprises a geometric feature formed into the metal material. 
     
     
       13. The electronic device of  claim 9 , wherein:
 the pigment particles are titanium dioxide particles; and 
 the marking further comprises a color feature formed, in part, at an interface between the first layer and the second layer. 
 
     
     
       14. The electronic device of  claim 9 , wherein the multilayer coating does not include visible cracks along the recess wall. 
     
     
       15. A method comprising:
 providing a device component of an electronic device, the device component comprising:
 a metal substrate; and 
 a coating layer formed along a surface of the metal substrate and comprising:
 a first layer disposed over the surface of the metal substrate and comprising a polymer binder and inorganic pigment particles dispersed within the polymer binder; and 
 a second layer disposed over the first layer and comprising a transparent polymer defining at least a portion of an exterior surface of the electronic device; and 
 
 
 producing a laser-formed relief feature included in a marking formed along the exterior surface of the electronic device, the operation of producing the laser-formed relief feature comprising:
 removing, using a first laser, a portion of the coating layer to:
 form at least one recess wall of the laser-formed relief feature, the at least one recess wall partially defining a recess extending through the first layer and the second layer; and 
 expose a portion of the metal substrate; and 
 
 modifying the portion of the metal substrate, using a second laser, to create a recessed marking feature of the laser-formed relief feature, the recessed marking feature visually distinct from an adjacent portion of the coating layer and defining a bottom of the recess. 
 
 
     
     
       16. The method of  claim 15 , wherein the first laser produces pulses having a duration in a femtosecond range and a wavelength in an ultraviolet range. 
     
     
       17. The method of  claim 15 , wherein the second laser produces pulses having a duration in a nanosecond range and a wavelength in an infrared range. 
     
     
       18. The method of  claim 15 , wherein the operation of removing the portion of the coating layer produces a crack-free coating region along the at least one recess wall. 
     
     
       19. The method of  claim 15 , wherein the recessed marking feature comprises a groove extending into the metal substrate and defining a pair of groove walls. 
     
     
       20. The method of  claim 15 , wherein:
 the recessed marking feature includes an oxide layer formed over the metal substrate; and 
 a color of the recessed marking feature is due, at least in part, to a thickness of the oxide layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a non-provisional patent application of and claims the benefit of U.S. Provisional Patent Application 62/693,842, filed Jul. 3, 2018 and titled “Controlled Ablation and Surface Modification for Marking an Article,” U.S. Provisional Patent Application 62/753,027, filed Oct. 30, 2018 and titled “Controlled Ablation and Surface Modification for Marking an Article,” and U.S. Provisional Patent Application 62/816,769, filed Mar. 11, 2019 and titled “Controlled Ablation and Surface Modification for Marking an Electronic Device,” the disclosures of which are hereby incorporated herein by reference in their entireties. 
    
    
     FIELD 
     The described embodiments relate generally to forming a marking on an article or component for an electronic device. More particularly, the present embodiments relate to forming a marking including a relief feature which extends at least partially through a coating that defines an exterior surface of the article or component of the electronic device. 
     BACKGROUND 
     Articles such as electronic devices generally include an exterior component, such as a housing, that may be marked or printed. Some traditional marking techniques form letters or glyphs using lines of ink. Such markings may be subject to wear over the lifetime of the device. 
     Embodiments described herein are directed to markings for articles such as electronic devices that may have advantages as compared to markings produced by some traditional techniques. In embodiments described herein, the article includes a coating along an exterior surface and the marking includes a marking feature recessed with respect to the coating. A recessed marking feature may provide a color or other visual attribute to the marking. The markings described herein can provide a distinctive appearance to the article and may also provide improved durability over some traditional ink or paint based marking techniques. In general, the markings formed using the described techniques may not suffer from the drawbacks associated with some traditional ink-based marking techniques. 
     SUMMARY 
     Embodiments described herein relate to markings formed along an exterior surface of an article, articles including the markings, and techniques for forming the markings. The marking may be in the form of an image, a pattern, text, a glyph, a symbol, an indicia or a geometric shape. In embodiments, the marking extends through a coating defining an exterior surface of the article and visually contrasts with the coating. The marking may be formed using a laser to allow precise removal of the coating in the marking area and to give a color or other visual attribute to the marking. 
     In aspects of the disclosure, the article comprises a device component and the marking is formed on the device component. In additional aspects, the article is an electronic device or a component of an electronic device. The device component may comprise a metal material, such as a metal or a metal alloy. The device component may further comprise a coating formed over a surface, such as a front surface, of the metal material. The coating may be a multilayer coating. 
     In further aspects, the marking comprises a recessed marking feature which provides a color or other visual attribute to the marking. By the way of example, the recessed marking feature is recessed with respect to an exterior surface of the article and defined along an exterior surface of the metal material. 
     In further aspects, the recessed marking feature is included in a relief feature, which may be laser-formed. The relief feature may further include at least one recess wall that partially defines a recess. The recess may extend through all or a portion of a thickness of the coating. In additional aspect, the marking may comprise additional features, such as a laser-formed color feature formed within the coating. 
     In embodiments, an electronic device comprises a device component comprising a metal substrate, a coating layer formed along at least a front surface of the metal substrate, and a marking. The coating layer comprises a first layer disposed over the front surface of the metal substrate and comprising a polymer binder and inorganic pigment particles dispersed within the polymer binder. The coating layer further comprises a second layer disposed over the first layer and comprising a transparent polymer defining at least a portion of an exterior surface of the electronic device. The marking is formed along an exterior surface of the electronic device and comprises a laser-formed relief feature. The laser-formed relief feature has at least one recess wall partially defining a recess extending through the first layer and the second layer of the coating. The laser-formed relief feature further has a recessed marking feature defining a bottom of the recess and visually distinct from an adjacent portion of the coating layer. 
     The recessed marking feature may include a geometric feature, a color feature, and/or a texture feature formed in the front surface of the metal substrate as described in the present disclosure. The recessed marking feature may include at least one geometric feature, such as a groove or channel, formed into the exterior surface of the metal material. As another example, the recessed marking feature may include a color feature having a structural color. For example, a metal oxide layer may be formed on the exterior surface of the device component and have a thickness which imparts a color to the marking (marking color), such as through interference of light. As an additional example, the recessed marking feature may include a texture feature, such as a surface finish defining a roughness of the recessed marking feature. The recessed marking feature may also include combinations of these features. In aspects described herein, the marking comprises at least two recessed marking features. 
     In additional embodiments, an electronic device comprises a device component comprising a metal material, a multilayer coating formed over a surface of the metal material, and a marking formed into the multilayer coating. The multilayer coating comprises a first layer disposed over the surface of the metal material and comprising a binder and pigment particles dispersed within the binder. The multilayer coating further comprises a second layer disposed over the first layer and comprising a transparent polymer. The marking comprises a first recessed marking feature along a surface of the metal material and visually distinct from the multilayer coating. The marking further comprises a laser-formed relief feature at least partially surrounding the first recessed marking feature. The relief feature has a recess wall partially defining a recess, the recess extending through the first layer and the second layer of the multilayer coating. The laser-formed relief feature further has a second recessed marking feature visually distinct from an adjacent portion of the multilayer coating and defining, in part, a bottom of the recess. 
     Each of the first and the second recessed marking features may include a geometric feature, a color feature, and/or a texture feature as described in the present disclosure. The second recessed marking feature may be visually distinct from the first recessed marking feature. The first recessed marking feature may also define, in part, a bottom of the recess. For example, the first recessed marking feature may include a color feature and the second recessed marking feature may include a geometric feature which forms a complete or partial perimeter around the first recessed marking feature. 
     The present disclosure also relates to methods for forming a marking along an exterior surface of an article such as an electronic device or a component for an electronic device. In aspects of the disclosure, a multilayer coating defines the exterior surface of the electronic device and the marking includes a laser-formed relief feature comprising a recessed marking feature and a recess wall at least partially defining a recess in at least a portion of the multilayer coating. 
     In embodiments, the methods of forming the marking produce little, if any, damage to the multilayer coating adjacent the recessed marking feature. For example, the methods may not change the color and/or texture of the recess wall of the relief feature to an extent visually discernable by the human eye at a normal viewing distance. As another example, the methods n may produce a recess wall and an adjacent portion of the multilayer coating which have no cracks visually discernable to the human eye at a normal viewing distance. 
     In aspects of the disclosure, the relief feature may be formed using a laser-based treatment as described herein. The laser-based treatment may include at least two different laser-based treatment operations. The at least two different laser-based treatment operations may involve two different lasers or a single laser operated at two different process conditions. 
     In embodiments, a method for forming a marking comprising a relief feature along an exterior surface of an electronic device comprises removing, using a first laser, a portion of a multilayer coating to form a recess through the multilayer coating and expose a metal portion of a substrate. The multilayer coating is formed over a surface of the substrate and comprises a first layer comprising a binder and inorganic pigment particles dispersed within the binder and a second layer comprising a transparent polymer. The method further comprises modifying the metal portion, using a second laser, to create a recessed marking feature of the relief feature. The recessed marking feature comprises at least one of a geometric feature formed into the metal portion or a color feature formed on the metal portion. 
     The operation of modifying the metal portion may include one or more of laser texturing and laser coloring the metal portion. The operation of modifying the metal portion may further include laser shaping the metal portion. As previously discussed, in embodiments the operation of modifying the metal portion produces little, if any, damage to the multilayer coating adjacent the recessed marking feature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like elements. 
         FIG. 1A  shows an example article with a marking in accordance with embodiments herein. 
         FIG. 1B  shows an enlarged view of the marking of  FIG. 1A  showing a top view of a relief feature. 
         FIG. 1C  shows an enlarged view of the marking of  FIG. 1A  showing a top view of another relief feature. 
         FIG. 1D  shows an example of a cross-sectional view of the marking of  FIG. 1C . 
         FIG. 1E  shows another example of a cross-sectional view of the marking of  FIG. 1C . 
         FIG. 2  shows a schematic cross-sectional view of an example marking comprising a recessed marking feature including a geometric feature. 
         FIG. 3  shows a schematic cross-sectional view of an example marking comprising a recessed marking feature including multiple geometric features. 
         FIG. 4  shows a schematic cross-sectional view of another example marking comprising a recessed marking feature including a geometric feature. 
         FIG. 5  shows a schematic cross-sectional view of an additional example marking comprising a recessed marking feature including a geometric feature. 
         FIG. 6A  shows a schematic cross-sectional view of an example marking comprising a recessed marking feature including a metal oxide layer. 
         FIG. 6B  shows a schematic cross-sectional view of another example marking comprising a recessed marking feature including a metal oxide layer. 
         FIG. 7  shows a schematic cross-sectional view of an example marking comprising a geometric feature and a recessed marking feature including a metal oxide layer. 
         FIG. 8  shows a schematic cross-sectional view of an additional example marking comprising a recessed marking feature including a geometric feature and a metal oxide layer. 
         FIG. 9  shows a schematic cross-sectional view of a further example marking comprising a recessed marking feature including a geometric feature and a metal oxide layer. 
         FIG. 10A  shows an enlarged view of an additional example marking showing a top view of a relief feature. 
         FIG. 10B  shows a schematic cross-sectional view of the marking of  FIG. 10A . 
         FIG. 11A  shows an enlarged view of a further example marking showing a top view of a relief feature. 
         FIG. 11B  shows an enlarged view of another example marking showing a top view of a relief feature. 
         FIG. 11C  shows an enlarged view of an additional marking showing a top view of a relief feature. 
         FIG. 12  shows a flowchart of an example process for making a marking. 
         FIGS. 13A, 13B, 13C, and 13D  schematically show stages in an example process for making a marking. 
         FIG. 14  shows a flowchart of an additional example process for making a marking. 
         FIG. 15  shows a flowchart of another example process for making a marking. 
         FIG. 16  shows a schematic representation of an electronic device. 
     
    
    
     The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures. 
     Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented therebetween, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred implementation. To the contrary, the described embodiments are intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the disclosure and as defined by the appended claims. 
     The following disclosure is generally related to forming a marking along an exterior surface of an article. In embodiments, the marking extends through a coating defining the exterior surface of the article. The marking may include laser-formed relief feature having a marking feature which is at least partially recessed with respect to the coating. The relief feature may further include a recess wall that partially defines a recess. In aspects of the disclosure, the article is an electronic device or a component of an electronic device. 
     The techniques described herein use a laser to form the marking. In aspects of the disclosure, the techniques use a laser to form a relief feature. The laser parameters may be specially adapted to limit or prevent visual defects or cracks within the coating due to thermal effects from the laser. Further, techniques described herein may be adapted to limit removal and/or roughening of a metal material underlying the coating during formation of the recess. Therefore, the laser-based marking techniques described herein may provide an advantage over some traditional techniques which may produce greater disruption of the coating and/or the surface of the metal substrate. As examples, the laser-based marking techniques described herein may provide an advantage over some mechanical engraving or chemical etching techniques. In addition, the laser-based techniques described herein can form recessed marking features having at least one dimension which is micro-scale or milli-scale. 
     The marking may be in the form of an image, a pattern, text, a glyph, a symbol, an indicia, or a geometric shape. As examples, geometric shapes include, but are not limited to lines, curves, and shapes such as circles, ovals, and polygons. Polygons include, but are not limited to, triangles, squares, rectangles, pentagons, and hexagons. 
     The marking may comprise a relief feature which is, in part, recessed with respect to an exterior surface of the coating. For example, the recessed marking feature may be recessed with respect to the exterior surface of the coating. The relief feature may have a depth less than 1 mm, less than 500 μm, from about 100 μm to about 500 μm, from about 50 μm to about 150 μm, or from about 5 μm to about 30 μm. In aspects, the relief feature has a width from about 20 μm to about 100 μm, less than about 1 mm, less than about 1 cm, or less than about 5 cm. Typically, the relief feature is a blind feature and does not extend through the device component. 
     The relief feature may further comprise one or more recess walls defining a recess in the coating, with the recessed marking feature positioned at least partially below the recess. For example, the relief feature may comprise a pair of recess walls defining a recess in the coating. The recessed marking feature may define a bottom of the recess. The relief feature may further comprise a perimeter at the exterior surface of the coating and may be formed using a laser-based treatment as described herein. 
     The visual appearance of the marking and the coating may differ in order to provide visual contrast. For example, the recessed marking feature may provide a reflectance and/or color which differs from that of an exterior surface of the coating. In addition, the recessed marking feature may include a geometric feature which is visually discernable. The recessed marking feature may be formed along an external surface of a metal material. The metal material may form a portion or a whole of a substrate. For example, the substrate may be formed of a metal material, in which case the substrate may be referred to as a metal substrate. The recessed marking feature may also be formed along an external surface of a metal portion of the substrate. 
     By way of example, visually discernable geometric features may be formed as depressions, protrusions, holes, or other geometric forms relative to an exterior surface of the metal material. By the way of example, a geometric feature may have a depth of from 10 μm to 500 μm. The recessed marking feature may include one or more grooves or channels forming a depression in an exterior surface of the metal material. In addition, the recessed marking feature may include a depression whose perimeter defines a circular, oval, or polygonal shape. 
     In embodiments, a groove or channel may have a width that is narrow relative to a width of the recessed marking feature. For example, a groove or channel may have a width that is less than about 20% or less than about 10% of the width of the recessed marking feature. As an additional example, a groove or channel may have a width that is greater than about 20% of the width of the recessed marking feature and less than or equal to the width of the recessed marking feature. As further examples, a groove may be v-shaped or u-shaped in cross-section  123 . As used herein, the terms “about” and “approximately” are used to account for relatively small variations, such as a variation of +/−10%, +/−5%, or +/−2%. As examples, a width of a groove or channel may be greater than its depth, equal to its depth, or less than its depth. In embodiments, a depth of a groove or channel is less than a thickness of the coating. 
     A groove or channel may take a variety of forms. For example, a groove may form a perimeter around a portion of the recessed marking feature. Additional features of the marking, such as a texture feature (e.g., a surface finish) or a color feature (e.g., a metal oxide layer), may therefore be inward from this perimeter. The recessed marking feature may also include a pattern of multiple grooves. For example, the recessed marking feature may include multiple grooves aligned to form a hatching pattern. As another example, the marking feature may include a first set of grooves aligned to form a first hatching pattern and a second set of grooves aligned to form a second hatching pattern which is angled with respect to the first hatching pattern, thereby forming a crosshatching pattern. As another example, a geometric feature such as an angle or groove may be formed in the surface of the metal material in order to present a region of the recessed marking, at a particular angle with respect to a horizontal plane. 
     In additional aspects, a geometric feature may provide a degree of isolation between a recess wall of the relief feature and a region of the recessed marking feature which is to undergo a laser-based treatment. Inclusion of such a geometric feature in the recessed marking feature can minimize damage to the recess wall of the relief feature during the laser-based treatment. Suitable geometric features for this purpose include, but are not limited to an angle, a curve, or a groove formed in the surface of the metal material proximate the recess wall of the relief feature. For example, an angle geometric feature may define an obtuse angle (e.g., angle from 110 degrees to 160 degrees) with respect to the region of the recessed marking feature which is to undergo a laser-based treatment. 
     In aspects of the disclosure, a color feature produces a structural color. Structural colors may result from a variety of effects including interference of light, diffraction of light, and combinations thereof. In embodiments, the color feature includes a metal oxide layer configured to produce a color through interference. The desired color may be produced at a desired viewing angle. In additional embodiments, the color feature includes diffraction features configured to produce a color through diffraction, such as laser induced periodic surface structures. In embodiments, the color feature does not include a paint or an ink. 
     The color of a color feature may be characterized using a color model. For example, in the hue-saturation-value (HSV) color model, the hue relates to the wavelength(s) of visible light observed when the color feature is viewed (e.g., blue or magenta) and the value relates to the lightness or darkness of a color and relates to the amount of light reflected from the color feature. The saturation relates to the perceived colorfulness as judged in proportion to its brightness. As another example, coordinates in CIEL*a*b* (CIELAB) color space may be used to characterize the color, wherein L* represents brightness, a* the position between red/magenta and green, and b* the position between yellow and blue. A broadband or semi-broadband illuminant may be used to determine the color of the color feature. For example, a CIE illuminant may be used. 
     Further, color(s) may be characterized in terms of perceived wavelengths of visible light (e.g. from about 380 nm to about 750 nm). Chromatic colors have a hue (such as predominantly red, blue, yellow or green). A spectral color is present in the visible spectrum and is associated with a relatively narrow band of wavelengths. Non-spectral colors may include achromatic colors (such as white, gray or black), colors that are mixtures of spectral colors (such as violet-red colors), colors that are mixtures of spectral colors with achromatic colors, and metallic colors. For example, a violet color may be associated with light having a wavelength from about 380 nm to about 450 nm, a blue color may be associated with light having a wavelength between about 450 nm to about 495 nm, a cyan color may be associated with light having a wavelength from about 490 nm to about 520 nm, a green color may be associated with light having a wavelength between 495 nm and 570 nm, a yellow color may be associated with light having a wavelength from about 570 nm to about 590 nm, an orange color may be associated with light having a wavelength from about 590 nm to 620 nm, and a red color may be associated with light having a wavelength from about 620 nm to about 750 nm. In addition, a magenta color may be associated with light having predominantly red wavelengths and blue/violet wavelengths. 
     In additional embodiments, the spectral reflectance curve of a marking feature may be used to describe its optical properties. The spectral reflectance curve may be obtained over the visible spectrum or over a broader range, such as from about 400 nm to about 1500 nm. In addition, the extent of specular reflection or directionality of the reflectance may be measured. 
     A color feature having a metallic color may have a metallic luster. For example, a metallic color with a metallic luster may have a spectral reflectance curve with a relatively high reflectance over a relatively large portion of the visible spectrum and may have predominantly specular reflection. In embodiments, a color feature with a metallic luster has a spectral reflectance of at least 80%, at least 70%, at least 60%, at least 50%, or at least 40% over at least a portion of the visible spectrum. In embodiments, a metallic color may have a largely gray or “silvery” appearance when the spectral reflectivity is substantially uniform across the visible spectrum. The laser coloring process may produce a structural color which modifies a gray or “silvery” appearance of a metal. For example, a laser coloring process may change the spectral reflectance curve to decrease the reflectance in at least a portion of the blue and/or the green portion of the visible spectrum, thereby producing an at least partially golden color feature. 
     In embodiments, a color feature may include an oxide layer which gives the recessed marking feature a color (i.e., a marking color). The metal oxide may be a thermally grown metal oxide. In additional embodiments, the oxide layer may give the recessed marking feature more than one color. In some aspects, a first portion of the oxide layer may provide a first marking color and a second portion of the oxide layer may provide a second marking color. Alternately, the first portion of the oxide layer may be referred to as a first oxide layer and the second portion of the oxide layer may be referred to as a second oxide layer. 
     In embodiments, a portion of the oxide may have a thickness or a thickness range configured to produce a desired hue or combination of hues, such as at a desired viewing angle. In additional aspects, the thickness of the oxide layer may vary such that the color feature blends different colors. For example, when the size of the recessed marking feature is significantly greater than the spot size of the laser used to form the color feature, differences in heating of the metal substrate may produce some variation in the oxide layer thickness over the recessed marking feature. 
     A texture feature may include a texture formed into the external surface of the metal material. In embodiments, the texture feature includes a surface finish. The surface finish may define, at least in part, a reflectance of the recessed marking feature. As an example, the surface finish may be characterized by the roughness of the external surface of the metal material. In additional embodiments, a texture feature may include fine geometric features, such as hatching lines, formed into the metal material. The texture may be coated with a relatively thin oxide layer formed during the texturing process. In embodiments, the relatively thin oxide layer may produce little, if any, color effect and may have a thickness less than 5 nm, less than 3 nm, or less than 2 nm. 
     In embodiments, the laser-formed relief feature extends through a multilayer coating. For example, a coating layer may comprise a first layer disposed over the metal material and a second layer disposed over the first layer. In further aspects, the coating layer consists of or consists essentially of the first layer and the second layer. The first coating layer may comprise pigment particles and a binder. The pigment particles may be inorganic pigment particles, such as metal oxide particles or carbon particles. In some aspects of the disclosure, the inorganic pigment particles give the first coating layer a white color or a black color. The binder may be a polymer or resin binder, such as an acrylate or an epoxy binder. The pigment particles may be dispersed within the binder. 
     The second coating layer may comprise a transparent polymer. The transparent polymer may have a hardness and/or an abrasion resistance greater than that of the first coating layer. For example, the second coating layer may comprise an acrylate polymer or an epoxy polymer. The second coating layer may also comprise filler materials, such as nanoscale inorganic or diamond materials. By the way of example, the multilayer coating may have a thickness less than 1 mm, such as from about 50 μm to about 500 μm. 
     In additional aspects, the marking further comprises other features. In embodiments, a laser-formed color feature may be formed in a layer of the coating. For example, exposure of pigment particles in the first coating to a laser beam may induce a color change in the pigment particles which can be used to form a marking. As an additional example, exposure of titanium dioxide particles in the first coating layer to the laser beam can produce a darker color feature within the coating. 
     These and other embodiments are discussed below with reference to  FIGS. 1A-16 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1A  depicts a simplified example of an article. In some embodiments, the article  100  is an electronic device incorporating one or more electronic components. The article  100  may also be a component of an electronic device including, for example, a housing, enclosure, or cover of an electronic device. The electronic device may be a portable electronic device or other suitable electronic device. For example, the portable electronic device may be a laptop computer or a tablet. As additional examples, the portable electronic device may be a wrist-watch, a media player, a mobile phone, a camera, a headphone device, an earpiece device, a remote control, an identifier (e.g., a card), or other electronic device. 
     In additional aspects of the disclosure, the article  100  may include a data bearing record, but need not incorporate an electronic component. As examples, the article  100  may have optical features and/or magnetic features which are capable of storing data and which are readable by a component of a data processing system. The article  100  may be portable. As example, the article  100  may be part of a laptop computer, a tablet, a wrist-watch, a media player, a mobile phone, a camera, a headphone device, an earpiece device, a remote control or may be an identifier (e.g., a card), or other such article. 
     As shown in  FIG. 1A , the article  100  has an exterior surface  102  and a marking  120  has been formed along exterior surface  102 . The location of the marking is not limited, and marking  120  may be formed on the exterior surface  106 , the exterior surface  104 , and/or the exterior surface  102  of the article  100 . As examples, the exterior surface  102  may be a front or a back surface of the device and the exterior surface  104  may be a side surface of the device. As shown, the article  100  includes a coating  130  which defines at least a portion of exterior surface  102 . The coating  130  may be formed along an exterior surface  112  of the metal substrate  140 , as shown in  FIG. 1D . 
     The article  100  further includes a device component  110 . The device component  110 , alone or in combination with other device components, may define an internal volume configured to receive one or more internal components of the article  100 . For example, the device component  110  may be a component of a housing, enclosure, or cover for the article  100 . The internal components of the article  100  may include various electronic components. For example, the electronic components may include one or more of a processor, control circuitry, a sensor, memory, and a battery. An example electronic device is described below with respect to  FIG. 16  and the description provided there is generally applicable to articles as described herein. 
     As shown in  FIG. 1A , the marking  120  further includes a first relief feature  150  and a second relief feature  160 . The first relief feature  150  includes a perimeter  152  at the exterior surface  102  of the article  100 . The second relief feature  160  includes an interior perimeter  161  and an exterior perimeter  162  at exterior surface  102 ; the interior perimeter  161  forms an outline around a portion of the coating  130 . The visual appearance of the first relief feature  150  and the second relief feature  160  may differ from each other or may be the same. The visual appearance of each of the first relief feature  150  and the second relief feature  160  differs from that of the coating  130 . For example, the first relief feature  150  and the second relief feature  160  may be visually distinct from a portion of the coating layer adjacent to the laser-formed relief feature. For example, an adjacent portion of the coating may include an exterior surface of the coating layer and may form a perimeter around the relief feature. 
       FIG. 1B  shows an enlarged top view of the relief feature  150  of  FIG. 1A  (Detail  1 - 1 ). As shown in  FIG. 1B , the relief feature  150  comprises a recessed marking feature  156 . The relief feature  150  also comprises a perimeter  152  defined by the exterior surface of the coating  130 . The recessed marking feature  156  may have a visual appearance different from that of the coating  130  so that it is visually distinct from an adjacent portion of the coating (e.g., the coating adjacent perimeter  152 ). In some embodiments, the recessed marking feature may have at least one dimension, such as a width, which is micro-scale (having a dimension greater than or equal to 1 micron and less than 1 millimeter). In additional embodiments, the recessed marking feature may have at least one dimension, such as a width, which is milli-scale (having a dimension greater than or equal to 1 millimeter and less than 1 centimeter). 
       FIG. 1C  shows an enlarged top view of the relief feature  160  of  FIG. 1A  (Detail  2 - 2 ). As shown in  FIG. 1C , the relief feature  160  comprises a recessed marking feature  166 . The recessed marking feature  166  may have a visual appearance different from that of the coating  130 . The relief feature  160  also comprises an interior perimeter  161  and an exterior perimeter  162  defined by the exterior surface of the coating  130 . 
       FIG. 1D  is an example cross-sectional view of the relief feature  160  of  FIG. 1C .  FIG. 1D  provides an example of a fine marking which can be produced using a laser-based technique to remove some of the coating  130  and expose some of a metal substrate  140 . As shown, removal of some of the coating does not significantly distort the remainder of the coating or the underlying metal substrate. Although the exposed metal substrate  140  is depicted as being flat, this is not limiting, as described below with respect to the examples of  FIGS. 1E, 2-5, 6B, 7-9 , and  10 B. In additional examples, the metal substrate may be referred to as a metal material. Further, a metal oxide layer may be formed on the exposed metal substrate as described below with respect to  FIGS. 6A-9 . 
     The relief feature  160  comprises a recessed marking feature  166 , which is recessed with respect to the exterior surface  102  of the article  100 . The recessed feature  166  is positioned below a recess  163  in the coating  130  and has a width W. The coating  130  around the recess  163  defines recess walls  164  (side walls) of the relief feature  160 . Although the recess walls  164  are shown as forming an angle of about 90° with respect to surface  112 , this is not limiting, as shown with respect to  FIG. 1E . An exterior surface of the coating  130  defines at least a portion of the exterior surface  102  of the article  100 . 
     As shown in  FIG. 1D , the coating  130  is formed along an exterior surface  112  of the metal substrate  140  and the recessed marking feature  166  is formed along an exterior surface  114  of the metal substrate  140 . The exterior surface  112  may be a first portion and the exterior surface  114  may be a second portion of the exterior or outer surface of the metal substrate  140 . The exterior surface  114  is not required to be at the same height as the exterior surface  112 . For example, laser-based treatment of exterior surface  114  may cause the exterior surface  114  to be recessed with respect to the exterior surface  112 . In some embodiments, the exterior surface  114  is recessed by 5 μm or less, 3 μm or less, 2 μm or less, or 1 μm, or less with respect to the exterior surface  112 . As for the exterior surface  102 , the exterior surface  114  may be a front, a back, or a recess wall of the metal substrate. 
     The exterior surface  114  may have a texture which gives the recessed marking feature a visual attribute. For example, the exterior surface  114  may have a surface finish with a roughness corresponding to that of a polished surface. The roughness of the exterior surface  114  may be from about 1 μm to about 5 μm. In additional example, the roughness of the exterior surface  114  may be greater than 5 μm, or greater than 10 μm. One measure of surface roughness is the parameter Ra which is a measure of the amplitude of the roughness profile (arithmetic average value of roughness determined from deviations about a center line). Another parameter is Sm, which is the mean spacing between peaks in the roughness profile. Reflectance may also be used as a measure of surface roughness. The foregoing discussion of texture and surface finish is not limited to the example of  FIG. 1D , but applies more generally to texture features of the present disclosure. 
     Further, the exterior surface  114  may include an oxide layer which gives the recessed marking feature a marking color. The metal oxide may be a thermally grown metal oxide. For example, the metal oxide layer may be thermally grown on a metal material by laser heating of the substrate. Suitable metal materials include, but are not limited to, titanium alloys, steels, or zirconium based, titanium-based, or iron-based bulk solidifying alloy substrates. In some embodiments, the metal material is predominantly crystalline and may have percentage of crystalline phase(s) greater than 50%, 60%, 70%, 80%, or 90%. In some embodiments, the thermally grown metal oxide may have a porosity less than that of an anodically grown porous metal oxide. In embodiments, the metal oxide may comprise a titanium oxide, an iron oxide, a chromium oxide, a zirconium oxide or combinations thereof. 
     The thickness of a metal oxide layer can affect the color of the recessed marking feature in several ways. For example, a metal oxide layer may display a color as a result of interference of light reflected from the metal oxide and the underlying metallic substrate. Typically the interference color displayed depends upon the thickness of the metal oxide. A metal oxide having a thickness too great to display interference colors may appear dark. When the metal oxide is very thin (or is not present), the recessed marking feature may appear bright or metallic. A variety of colors may be obtained, including, but not limited to, blue, purple, pink, red, orange, yellow, gold, brown, and green. Suitable thicknesses of the metal oxide layer to achieve a color from light interference may depend on the composition and crystallinity of the layer as well as the desired color to be achieved. As an example, a thickness of the metal oxide layer may be from 50 nm to 500 nm to obtain a color through interference of light. The foregoing discussion of color features including a metal oxide layer is not limited to the example of  FIG. 1D , but applies more generally to color features of the present disclosure. 
     The coating  130  may be a multilayer coating. As shown in  FIG. 1D , the coating  130  includes a first coating layer  134  having a thickness T 1  and a second coating layer  136  having a thickness T 2 . The thickness of the first coating layer may be greater than that of the second coating layer. In some embodiments the combined thickness of the coating layers is from 50 μm to 500 μm or from 100 μm to 300 μm. The first coating layer  134  is disposed over the exterior surface  112  of the metal substrate  140  and, as shown in  FIG. 1D , may contact the exterior surface  112  at an interface between the coating  130  and the metal substrate  140 . The second coating layer  136  is disposed over the first coating layer  134 . In some instances, the first coating layer  134  may be positioned over or may include a primer layer that coats or is positioned along a surface of the metal substrate  140 . The primer may include a polymer material including, for example, a urethane, acrylate or polymer material that facilitates adhesion to the metal substrate  140 . For purposes of this description, the first coating layer  134  may include a sub layer or layers of primers or other materials. That is, the first coating layer  134  is not necessarily homogenous or uniform throughout the thickness of the layer. 
     In embodiments, the first coating layer  134  comprises pigment particles and a polymer binder. As an example, the pigment particles may be inorganic pigment particles. Inorganic pigments include, but are not limited to, metal oxides such as titanium oxides (TiO 2 , Ti 2 O 3 ), zinc oxides (ZnO), manganese dioxide (MnO 2 ), and iron oxides (Fe 3 O 4 ). The particles may have a size range of 0.1 μm to 10 μm or 0.1 μm to 1 μm. Suitable polymers for the binder include, but are not limited to, single urethane polymers, multi urethane polymers, polyurethane, acrylate polymers, and epoxy polymers. The first coating layer may further comprise other additives in addition to the pigment. When the first coating layer  134  includes a sub layer of a primer, the first coating layer  134  may also include another sub layer comprising the pigment particles and the polymer binder. 
     In embodiments, the second coating layer  136  is transparent and comprises a transparent polymer. The transparent polymer may have a hardness and/or an abrasion resistance greater than that of the first coating layer. For example, the second coating layer may comprise an acrylate polymer or an epoxy polymer. The second coating may be a UV curable acrylic or other type of optically cured polymer. The second coating layer may also comprise filler materials, such as nanoscale inorganic or diamond materials. Nanoscale filler materials may have a diameter less than 100 nm or less than 50 nm. The second coating layer may also include various fillers including, for example, wax fillers, fluoropolymers, silica fillers, fluorosurfactant surface modifiers, and other materials. The second coating layer  136  may be treated to provide a particular surface texture or hand feel. In some instances, the second coating may provide a ceramic-like feel to the touch. For example, the second coating layer may include a UV curable acrylic having wax and silica fillers sufficient to simulate a smooth ceramic-like friction between the surface and the skin of a user&#39;s finger. The foregoing discussion of the first and second coating layers is not limited to the example of  FIG. 1D , but applies more generally to multilayer coatings of the present disclosure. 
       FIG. 1E  is another example cross-sectional view of the relief feature  160  of  FIG. 1B .  FIG. 1E  provides another example of a fine marking which can be produced using a laser-based technique to remove some of the coating  130  and expose some of the metal substrate  140 . As shown, removal of some of the coating does not significantly distort the remainder of the coating or the underlying metal substrate. Although the exposed metal substrate  140  is depicted as being concave, this is not limiting. Further, a metal oxide layer may be formed on the exposed metal substrate as described below with respect to  FIGS. 6A-9 . 
     The relief feature  160  comprises a recessed marking feature  166 , which is recessed with respect to the exterior surface  102  of the article  100 . The recessed feature  166  is positioned below a recess  163  formed at least in part in the coating  130  and the recessed feature  166  has a width W. The coating  130  around the recess  163  defines recess walls  164  (side walls) of the relief feature  160 . Although recess walls  164  are shown as having an oblique angle with respect to surface  112 , this is not limiting. An exterior surface of the coating defines at least a portion of the exterior surface  102  of the article  100 . 
       FIGS. 2-9 and 10B  illustrate schematic cross-sectional views of markings along exterior surfaces of example articles. By the way of example, the exterior surfaces of the articles of  FIGS. 2-9 and 10B  may be front surfaces of the article. Alternately, the exterior surfaces of the articles of  FIGS. 2-9 and 10B  may be a back surfaces or side surfaces of the article. In aspects of the disclosure, the articles of  FIGS. 2-9 and 10B  are electronic devices. 
       FIG. 2  shows a schematic cross-sectional view of an example marking  220  comprising a recessed marking feature  266  including a geometric feature  272 . As illustrated in  FIG. 2 , the geometric feature  272  is a groove formed in the exterior surface  214  of a metal material  240 , which may also be referred to as a metal substrate. As shown, the groove  272  is proximate the recess wall  264  of the relief feature  260 . The groove may have a rounded cross-sectional shape. As an example, a width of the groove may be about 10% or less of the width W of the recessed marking feature. 
     As shown in  FIG. 2 , the device component  210  includes the marking  220  along an exterior surface  202  of the article. The device component  210  includes a coating  230  along an exterior surface  212  of the metal material  240 . The coating includes a first layer  234  and a second layer  236 . The marking  220  comprises a relief feature  260  including a recessed marking feature  266  and recess wall  264 . The recess wall  264  at least partially defines a recess  263 . 
       FIG. 3  shows a schematic cross-sectional view of an example marking  320  comprising a recessed marking feature  366  including multiple geometric features  372 . As shown in  FIG. 3 , the geometric features  372  are grooves formed in an exterior surface  314  of a metal material  340 . As illustrated, the grooves  372  have an angular cross-sectional shape and are arranged to form a pattern. As an example, a width of the groove may be about 10% or less of the width W of the recessed marking feature. 
     As shown in  FIG. 3 , the device component  310  includes the marking  320  along an exterior surface  302  of the article. The device component  310  includes coating  330  along an exterior surface  312  of the metal material  340 . The coating includes a first layer  334  and a second layer  336 . The marking  320  comprises a relief feature  360  including recessed marking feature  366  and recess wall  364 . The recess wall  364  at least partially defines a recess  363 . 
       FIG. 4  shows a schematic cross-sectional view of another example marking  420  comprising a recessed marking feature  466  including a geometric feature  472 . As shown in  FIG. 4 , the geometric feature  472  is a channel (or groove) formed in an exterior surface  414  of a metal material  440  and having an angular cross-sectional shape. The channel  472  may have a width about equal to the width W of the recessed marking feature  466 . For example, a width of the geometric feature may be from about 80% to 100% of the width of the recessed marking feature  466 . An angle θ between walls  473   a  and  473   b  may be greater than about 45 degrees and less than 180 degrees or from about 60 degrees to about 120 degrees. The walls  473   a  and  473   b  may also be referred to as a pair of channel or groove walls. 
     As shown in  FIG. 4 , a device component  410  includes the marking  420  along an exterior surface  402  of the article. The device component  410  includes a coating  430  along an exterior surface  412  of the metal material  440 . The coating  430  includes a first layer  434  and a second layer  436 . The marking  420  comprises a relief feature  460  including the recessed marking feature  466  and a recess wall  464 . Recess wall  464  at least partially defines a recess  463 . 
       FIG. 5  shows a schematic cross-sectional view of an additional example marking  520  comprising a recessed marking feature  566  including a geometric feature  572 . As shown in  FIG. 5 , the geometric feature  572  is a channel formed in an exterior surface  514  of a metal material  540  and having a rounded cross-sectional shape. The rounded cross-sectional shape may be described by a first radius of curvature R 1  proximate the recess wall  564  and a second radius of curvature R 2  at the bottom of the channel. As shown, the second radius of curvature may have larger a magnitude than that of the first radius of curvature and may produce curvature of opposite direction or sign. The channel  572  may have a width about equal to the width W of the recessed marking feature  566 . For example, a width of the channel may be from about 80% to 100% of the width W of the recessed marking feature  566 . An angle θ between walls  573   a  and  573   b  may be greater than about 45 degrees and less than 180 degrees or from about 60 degrees to about 120 degrees. The channel  572  may have a depth D. 
     As shown in  FIG. 5 , a device component  510  includes the marking  520  along an exterior surface  502  of the article. The device component  510  includes a coating  530  along an exterior surface  512  of the metal material  540 . The coating includes a first layer  534  and a second layer  536 . The marking  520  comprises a relief feature  560  including the recessed marking feature  566  and the recess wall  564 . The recess wall  564  at least partially defines recess  563 . 
       FIG. 6A  shows a schematic cross-sectional view of an example marking  620  comprising a recessed marking feature  666  including a metal oxide layer  682  formed along an exterior surface  614  of a metal material  640 . As shown, the metal oxide layer  682  may have a thickness T and may extend across a width about equal to the width W of the recessed marking feature  666 . As previously discussed, the thickness of the metal oxide layer  682  may be configured to produce a structural color through interference. 
     As shown in  FIG. 6A , the thickness of the metal oxide layer  682  is substantially uniform. However, the illustration of  FIG. 6A  is not limiting and the thickness of the metal oxide layer may vary across the recessed marking feature. In embodiments, an oxide layer of varying thickness may be described by an average thickness or by a thickness range. In an embodiment, the extent of metal oxide thickness variation (e.g., the thickness range) may be small enough that the colors of the recessed marking feature are encompassed by single spectral color or hue (e.g., blue or green). In other embodiments, the recessed marking feature may display multiple distinct spectral colors or hues or a blending of different colors. In some embodiments, the desired viewing angle is about normal to the recessed marking feature  666 . 
     As shown in  FIG. 6A , a device component  610  includes the marking  620  along an exterior surface  602  of the article. A device component  610  includes a coating  630  along an exterior surface  612  of metal material  640 . The coating  630  includes a first layer  634  and a second layer  636 . The marking  620  comprises a relief feature  660  including the recessed marking feature  666  and a recess wall  664 . The recess wall  664  at least partially defines a recess  663 . As shown in  FIG. 6A  the exterior surface  614  under the metal oxide layer  682  may be recessed with respect to exterior surface  612  under the coating  630  due to growth of the metal oxide layer  682  into the metal material  640 . 
       FIG. 6B  shows a schematic cross-sectional view of an example marking  620  comprising a recessed marking feature  666  including a metal oxide layer  682  formed along an exterior surface  614  of a metal material  640 . As shown, the metal material  640  defines a channel  672  including walls  673   a ,  673   b . The metal oxide layer  682  is positioned within the channel, has a thickness T, and extends across a width W O  less than the width W of the recessed marking feature  666 . As previously discussed, the thickness of the metal oxide layer  682  may have a thickness or a thickness range configured to produce a desired hue or combination of hues, such as at a desired viewing angle. In embodiments, the desired viewing angle is about normal to the recessed marking feature  666 . 
     In addition, the walls  673   a ,  673   b  may each be viewed as angled geometric features which form a complete or partial perimeter around the metal oxide layer  682 . The walls  673   a ,  673   b  may define an obtuse angle (e.g., angle from 110 degrees to 160 degrees) with respect to a plane of the metal oxide layer  682  or the exterior surface  602 . Similarly, a complementary angle between walls  673   a ,  673   b  and the recess wall  664  may be an acute angle. 
     As shown in  FIG. 6B , a device component  610  includes the marking  620  along an exterior surface  602  of the article. The device component  610  includes a coating  630  along an exterior surface  612  of the metal material  640 . The coating includes a first layer  634  and a second layer  636 . The marking  620  comprises a relief feature  660  including the recessed marking feature  666  and a recess wall  664 . The recess wall  664  at least partially defines a recess  663 . As shown in  FIG. 6B  the exterior surface  614  under the metal oxide layer  682  is recessed with respect to exterior surface  612  under the coating  630 . 
     In additional embodiments, one or more geometric features may be formed in the metal oxide layer. The geometric feature may be any geometric feature described herein. The multiple geometric features may form a pattern. For example, multiple aligned grooves may form a hatching. 
     In additional aspects, a marking may include a recessed marking feature including a first color defined, in part, by a first metal oxide thickness and a second color defined, in part, by a second metal oxide thickness.  FIG. 7  shows a schematic cross-sectional view of an example marking  720  comprising a recessed marking feature  766  including a metal oxide layer  782   a ,  782   b  and a geometric feature  772   a ,  772   b . As shown, the metal oxide layer  782  may be formed along an exterior surface  714  of a metal material  740  and may include a first portion  782   a  having a first thickness T 1  and a second portion  782   b  having a second thickness T 2 . The first portion of the metal oxide layer may provide a first color and the second portion of the metal oxide layer may provide a second color. The first color and/or the second color may be defined, in part, by light interference. As previously discussed, the thickness of the first portion  782   a  and the second portion  782   b  of the oxide layer may have a thickness or a thickness range configured to produce a desired hue or combination of hues, such as at a desired viewing angle. In embodiments, the desired viewing angle is about normal to the recessed marking feature  766 . 
     Recessed marking features including a first metal oxide thickness and a second metal oxide thickness may be obtained by various methods. The second portion of the oxide layer may be grown to a different thickness than the first portion of the oxide layer. Further, laser ablation may be used to reduce the thickness of the oxide layer to the first and/or the second thickness. Alternately, the first portion of the oxide layer may be referred to as a first oxide layer and the second portion of the oxide layer may be referred to as a second oxide layer. 
     As shown in  FIG. 7 , the geometric feature  772   a ,  772   b  is a groove formed in an exterior surface  714  of the metal material  740  proximate the recess wall  764  of the relief feature. The geometric feature  772   a ,  772   b  is also shown as having a rounded cross-sectional shape.  FIG. 7  shows the groove as having two portions  772   a ,  772   b ; the groove shown in  FIG. 7  may form a full or partial loop. As shown, the metal oxide layer  782  is at least partially inward from portions  772   a ,  772   b  of the groove. The metal oxide layer  782  extends across a width about equal to a distance between portions  772   a ,  772   b  of the groove. 
     As shown in  FIG. 7 , a device component  710  includes the marking  720  along an exterior surface  702  of the article. The device component  710  includes a coating  730  along an exterior surface  712  of the metal material  740 . The coating includes a first layer  734  and a second layer  736 . The marking  720  comprises a relief feature  760  including the recessed marking feature  766  and a recess wall  764 . Recess wall  764  at least partially defines a recess  763 . When the metal oxide layer  782  grows upward from the level of the exterior surface  712 , a portion of the recess  763  may be to the side of, rather than above, the recessed marking feature  766 . 
       FIG. 8  shows a schematic cross-sectional view of an additional example marking  820 . Marking  820  includes a relief feature  860  comprising a geometric feature  872  and a recessed marking feature  866  including a metal oxide layer  882 . As shown, the metal oxide layer  882  is formed over the geometric feature  872  and has a thickness T. As previously discussed, the metal oxide layer  882  may have a thickness or a thickness range configured to produce a desired hue or combination of hues, such as at a desired viewing angle. In embodiments, the desired viewing angle is about normal to the coating  830 . 
     As shown in  FIG. 8 , the geometric feature  872  may be a channel formed in an exterior surface  814  of the metal material  840 . The channel  872  may have a cross-sectional shape which defines walls  873   a  and  873   b . An angle between the walls  873   a  and  873   b  may be greater than about 45 degrees and less than 180 degrees or from about 60 degrees to about 120 degrees. The channel feature  872  may have a width about equal to the width W of the recessed marking feature  866 , such as from about 80% to 100% of the width of the recessed marking feature  866 . 
     The metal oxide layer  882  is formed along an exterior surface  814  of metal material  840  and along at least a portion of the exterior surface of channel  872 . As shown, the metal oxide layer  882  extends across a width about equal to the width W of the recessed marking feature  866 . An exterior surface of the oxide layer  882  on wall  873   a  may form an angle with an exterior surface of the oxide layer  882  on wall  873   b  due to the underlying channel geometry. This angle may be greater than about 45 degrees and less than 180 degrees or from about 60 degrees to about 120 degrees. 
     As shown in  FIG. 8 , a device component  810  includes a marking  820  along an exterior surface  802  of the article. The device component  810  includes a coating  830  along an exterior surface  812  of a metal material  840 . The coating  830  includes a first layer  834  and a second layer  836 . The marking  820  comprises a relief feature  860  including the recessed marking feature  866  and a recess wall  864 . 
     In further aspects, a marking may include a recessed marking feature including a first color defined, in part, by a first metal oxide thickness along a first wall of a groove or channel and a second color defined, in part, by a second metal oxide thickness along a second wall of the groove or channel. An apparent color of the recessed marking feature may be due to a combined effect of the first color and the second color. The apparent color of such a recessed marking feature may depend upon viewing angle. For example, from some viewing angles approximately equal amounts of the first wall and the second wall may be visible, and both the first and the second colors may be visible as distinct colors. From other viewing angles, the visible amount of the first wall may be significantly less than that of the second wall, and the color of the recessed marking feature may be dominated by the first color or may appear to have the first color (and vice versa). The apparent color of the recessed marking feature may therefore appear to shift as the viewing angle is changed. 
       FIG. 9  shows a schematic cross-sectional view of an additional example marking  920 . The marking  920  includes a relief feature  960  comprising a geometric feature  972  and a recessed marking feature  966 . As shown in  FIG. 9 , the recessed marking feature  966  comprises a metal oxide layer including a first portion  982   a  having a first thickness T 1  and a second portion  982   b  having a second thickness T 2 . As shown, the first thickness is less than the second thickness. Metal oxide portions  982   a ,  982   b  are formed along an exterior surface  914  of a metal material  940  and along at least a portion of the exterior surface of the geometric feature  972 . As previously discussed, the thickness of the first portion  982   a  and the second portion  982   b  of the oxide layer may each have a thickness or a thickness range configured to produce a desired hue or combination of hues, such as at a desired viewing angle. In embodiments, the desired viewing angle is about normal to the coating  930 . 
     As shown in  FIG. 9 , the geometric feature  972  may be a groove formed in the exterior surface  914  of the metal material  940 . The groove  972  may have a cross-sectional shape which defines walls  973   a  and  973   b . An angle between the walls  973   a  and  973   b  may be greater than about 45 degrees and less than 180 degrees or from about 60 degrees to about 120 degrees. The groove  972  may have a width about equal to the width W of the recessed marking feature  966 , such as from about 80% to 100% of the width of the recessed marking feature  966 . 
     As shown, the metal oxide layer extends across a width about equal to the width W of the recessed marking feature  966 . An exterior surface of the oxide layer on wall  973   a  may form an angle with an exterior surface of the oxide layer on wall  973   b  due to the underlying groove geometry. This angle may be greater than about 45 degrees and less than 180 degrees or from about 60 degrees to about 120 degrees. 
     As shown in  FIG. 9 , a device component  910  includes the marking  920  along an exterior surface  902  of the article. The device component  910  includes a coating  930  along an exterior surface  912  of the metal material  940 . The coating includes a first layer  934  and a second layer  936 . The marking  920  comprises a relief feature  960  including the recessed marking feature  966  and a recess wall  964 . Recess wall  964  at least partially defines a recess  963 . 
     In additional aspects, a marking includes at least two recessed marking features. For example, a first recessed marking feature may define a first region which is visually distinct from the coating. Each of the first and the second recessed marking feature may include a geometric feature, a color feature, a texture feature, or a combination thereof. The second recessed marking feature may have a visual attribute different from the first recessed marking feature. The second recessed marking feature may at least partially surround the first recessed marking feature, or vice versa.  FIGS. 10A, 10B, 11A, 11B, and 11C  illustrate non-limiting examples of markings including two recessed marking features. 
     The first and the second recessed marking features may encompass equal or unequal portions of the marking. The visual attribute(s) of the larger of the first recessed marking feature and the second recessed marking feature may dominate the appearance of the marking. For example, if the second recessed marking feature is thin relative to the first recessed marking feature, the attributes of the first recessed marking feature may largely determine the appearance of the marking. For example, the second recessed marking feature may have a width less than that of the first recessed marking feature and may form a complete or partial perimeter around the first recessed marking feature. 
       FIG. 10A  shows an enlarged view of an additional example marking  1020  of  FIG. 1A  showing a top view of a relief feature  1050 . As shown in  FIG. 10A , the relief feature  1050  comprises recessed marking features  1056   a ,  1056   b . A shown, the recessed marking feature  1056   b  includes a texture feature and is visually distinct from a coating  1030 . The relief feature  1050  also includes a recessed marking feature  1056   a  which defines a perimeter at least partially surrounding the recessed marking feature  1056   b . The relief feature  1050  also includes a perimeter  1052  around recessed marking feature  1056  and defined by the coating  1030 . 
       FIG. 10B  shows a schematic cross-sectional view of the marking  1020  of  FIG. 10A . As illustrated in  FIG. 10B , the marking  1020  includes a relief feature  1050 . A recessed marking feature  1056   a  of the relief feature  1050  includes a channel  1072  formed in an exterior surface  1014   a  of a metal material  1040 . As shown, the channel  1072  is proximate a recess wall  1054  of the relief feature  1050 . 
     As shown in  FIG. 10B , the marking  1020  also includes a recessed marking feature  1056   b . The recessed marking feature  1056   b  includes a surface roughness formed in exterior surface  1014   b  of the metal material. The recessed marking feature  1056   b  may be wider than the recessed marking feature  1056   b.    
     As shown in  FIG. 10B , a device component  1010  includes the marking  1020  along an exterior surface  1002  of the article. The device component  1010  includes a coating  1030  along an exterior surface  1012  of the metal material  1040 . The coating includes a first layer  1034  having a thickness T 1  and a second layer  1036  having a thickness T 2 . The relief feature  1050  includes a recess wall  1054 . The recess wall  1054  at least partially defines a recess  1053 . 
       FIG. 11A  shows an enlarged view of a further example marking  1120  of  FIG. 1A  showing a top view of a relief feature  1150 . As shown in  FIG. 11A , the relief feature  1150  comprises recessed marking features  1156   a ,  1156   b . A shown, the recessed marking feature  1156   b  includes multiple grooves arranged in a hatching pattern and is visually distinct from a coating  1130 . The relief feature  1150  also includes a recessed marking feature  1156   a  which defines a perimeter at least partially surrounding the recessed marking feature  1156   b . The relief feature  1150  also includes a perimeter  1152  around the recessed marking feature  1156   a  and defined by the coating  1130 . 
     As shown in  FIG. 11B , relief feature  1150  comprises recessed marking feature  1150 . As shown in  FIG. 11B , relief feature  1150  comprises recessed marking features  1156   a ,  1156   b . A shown, recessed marking feature  1156   b  includes multiple grooves arranged in cross-hatching pattern and is visually distinct from coating  1130 . Relief feature  1150  also includes recessed marking feature  1156   a  which defines a perimeter at least partially surrounding recessed marking feature  1156   b . The relief feature  1150  also includes a perimeter  1152  around the recessed marking feature  1156   a  and defined by the coating  1130 . 
       FIG. 11C  shows an enlarged view of another marking of  FIG. 1A  showing a top view of a relief feature  1150 . As shown in  FIG. 11B , the relief feature  1150  comprises recessed marking features  1156   a ,  1156   b . Recessed marking feature  1156   b  includes multiple circular geometric features  1172  and is visually distinct from coating  1130 . Relief feature  1156  also includes recessed marking feature  1156   a  which defines a perimeter at least partially surrounding recessed marking feature  1156   b . The relief feature  1150  also includes a perimeter  1152  around the recessed marking feature  1156   a  and defined by the coating  1130 . 
     The current description also encompasses processes for forming a marking along an exterior surface of an article. The article may be an electronic device. The processes may be performed on an article comprising a device component. The device component may comprise a substrate comprising a metal material and may further comprise a coating disposed over an exterior surface of the substrate. The coating may be a multilayer coating as described herein comprising a first layer disposed over the metal material and a second layer disposed over the first layer. The electronic device may include markings formed along an external surface of the device component, within the coating, or a combination thereof. 
     In embodiments, the processes for forming a marking along an external surface of the device component comprise laser ablating the coating in the marking area to expose a metal portion of the device component and laser modifying the metal portion to create a recessed marking feature. The operation of laser modifying the metal portion may comprise at least one of laser texturing and laser coloring the metal portion. In addition, the operation of laser modifying the metal portion may comprise laser shaping the metal portion to form a geometric feature. For example, the metal portion may be laser shaped through ablation to form a depression; the depression may then be laser textured and/or laser colored. The metal portion may be laser textured through ablation, partial melting, or combinations thereof. In embodiments, the metal portion may be laser colored through annealing without substantial ablation or melting. 
       FIG. 12  illustrates a flowchart of an example process  1200  for forming a marking along an exterior surface of an article. Process  1200  may be used to form a relief feature having a recessed marking feature. The recessed marking feature may be formed along an exterior surface of substrate comprising a metal material; a texture feature and/or geometric feature may be formed in a metal portion of the substrate to produce a visual effect. As examples, process  1200  may be used to form the recessed marking features of  FIGS. 1D, 1E, and 2-5  along an exterior surface of the metal portion. As used herein, a metal portion may include a metal alloy portion. 
     Operation  1210  comprises laser ablating the coating in a marking area of the article. The marking area is along an exterior surface of the article defined by an exterior surface of the coating. As an example, operation  1210  comprises removing, using a first laser, a first portion of the coating which is located in the marking area. The operation of laser ablating the coating in the marking area may use a first laser. For example, the first laser may be a femtosecond laser producing pulses having an effective pulse duration in the femtosecond range. The first laser may produce a wavelength in the ultraviolet range (e.g., having a wavelength from about 200 nm to about 400 nm). Alternately, the first laser may produce a wavelength in the infrared range (e.g., having a wavelength from about 1 μm to about 5 μm). The first laser may be operated in a vector mode, a raster mode, or a combination thereof. 
     For example, a vector mode may be used to laser ablate an outline in the first portion of the coating and a raster mode may be used to laser ablate coating within the outline, thereby laser ablating a remainder of the first portion of the coating. In some embodiments, the wavelength used to ablate an outline in the first portion of the coating may be different than the wavelength used to remove a remainder of the first portion of the coating within the outline. 
     By the way of example, a laser used to ablate an outline in the first portion of the coating may have a pulse duration from about 200 fs to about 800 fs, an average power from about 0.5 W to about 15 W or about 1 W to about 10 W. The repetition rate may be from about 10 kHz to 750 kHz, from about 10 kHz to about 500 kHz, or from about 10 kHz to about 100 kHz. In some embodiments, the laser may be operated in burst mode, with each burst including multiple pulses. In embodiments, the number of pulses in the burst may be from 5 to 25. The scan speed may be from about 1 mm/sec to about 50 mm/sec. The laser used to form the outline may be operated in vector mode. 
     In addition, a laser operated to remove a remainder of the first portion of the coating may have an average power, a repetition rate and/or a scan speed higher than that used to form the outline. For example, the pulse duration may be from about 200 fs to about 800 fs, the average power may be from about 0.5 W to about 15 W or about 1 W to about 10 W. The repetition rate may be from about 50 kHz to about 1000 kHz or from about 200 kHz to about 750 kHz. In some embodiments, the laser may be operated in burst mode, with each burst including multiple pulses. In embodiments, the number of pulses in the burst may be from 5 to 25. The scan speed may be from about 100 mm/sec to about 1000 mm/sec, the hatch distance from about 5 μm to about 30 μm, and the number of passes from 1 to 8. The spot size may be from 10 μm to 50 μm. The laser used to remove the remainder of the first portion of the coating may be operated in raster mode. In embodiments, the same laser may be used to form the outline as to remove the remainder of the first portion of the coating or different lasers may be used. 
     As explained in further detail with respect to  FIGS. 13A and 13B , the operation of removing the first portion of the coating using the first laser may form a recess extending through the coating. A second portion (remainder portion) of the coating surrounds the recess and defines a recess wall. The operation of removing the first portion of the coating also exposes a metal portion of the substrate. The exposed metal portion is under the recess. The exposed metal portion may alternately be referred to as a metal portion. 
     In embodiments, the laser(s) used in operation  1210  may be operated under conditions which minimize damage to the coating defining and adjacent to the recess wall. The coating may be a multilayer coating including a first layer and a second layer as previously described. In an example, few, if any, visually observable cracks are produced in the second layer and/or the recess wall during operation  1210 . In some embodiments, heating of the second layer during operation  1210  may help prevent cracking of this layer. 
     As previously discussed, the process of forming a marking along an exterior surface of an article may comprise modifying the exposed metal portion, using a laser, to create a recessed marking feature of the relief feature. The operation  1220  of the process  1200  comprises laser texturing within the marking area of the article. The operation of laser texturing may form a texture feature, a geometric feature, or a combination thereof into the exposed metal portion. In some embodiments, the operation of laser texturing may also affect the color of the marking feature. For example, the surface roughness of the marking feature may affect the brightness or darkness of the marking feature. 
     The operation of laser texturing may use a second laser. For example, the second laser may be a femtosecond laser producing pulses having an effective pulse duration in the femtosecond range. For example, the femtosecond laser may be used to form one or more geometric features into the exposed metal portion (e.g., hatching as shown in  FIGS. 11A-11B ). The femtosecond laser may produce a wavelength in the infrared range. The second laser may be operated in a vector mode, a raster mode, or a combination thereof. The pulse duration may be from 200 fs to 800 fs, the average power may be from about 0.01 W to about 15 W, from about 1 W to about 15 W, or from about 0.01 W to about 5 W, and the repetition rate may be from about 50 kHz to about 750 kHz or from about 50 kHz to about 300 kHz. In some embodiments, the laser may be operated in burst mode, with each burst including multiple pulses. In embodiments, the number of pulses in the burst may be from 5 to 25. The scan speed may be from about 750 mm/sec to about 1500 mm/sec, the hatch distance up to 50 μm, and the number of passes from 1 to 25. The spot size may be from about 10 μm to about 50 μm. Some geometric features, such as those shown in  FIGS. 7 and 8 , may be formed using multiple passes of the second laser. In some embodiments, the operation of laser texturing includes multiple laser texturing operations at different laser operating conditions. 
     In some embodiments, a nanosecond laser producing pulses having an effective pulse duration in the nanosecond range may be used in addition to or as an alternate to a femtosecond laser. For example, the nanosecond laser may be used to polish the exposed metal portion, thereby modifying the roughness of the exposed metal portion. The laser may produce a wavelength in the near infrared range. The pulse duration may be from about 2 ns to about 300 ns, the average power may be from about 0.01 W to about 15 W, from about 0.01 W to about 5 W, or from about 1 W to about 10 W. The repetition rate may be from about 50 kHz to about 400 kHz. In some embodiments, the laser may be operated in burst mode, with each burst including multiple pulses. In embodiments, the number of pulses in the burst may be from 5 to 25. The scan speed may be from about 200 mm/sec to about 2000 mm/sec, the hatch distance from about 5 μm to about 30 μm, and the number of passes from 1 to 10. The spot size may be from about 10 μm to about 50 μm. 
     Process  1200  may optionally include operation  1230  of laser coloring the marking area. Operation  1230  may occur as part of an annealing operation. As an example, operation  1230  comprises modifying the exposed metal portion of the substrate, using a third laser, to create a color feature along an exterior surface of the metal portion. In embodiments, the operation of laser coloring the marking area produces a structural color. As previously discussed, structural colors may result from a variety of effects including interference of light, diffraction of light, and combinations thereof. 
     In embodiments, operation  1230  comprises thermally growing a metal oxide layer in the marking area of the article. The metal oxide layer may provide a structural color through interference of light. As an example, operation  1230  comprises modifying the exposed metal portion of the substrate, using a third laser, to create a metal oxide layer along an exterior surface of the metal portion. In some embodiments, the operation of thermally growing the oxide layer includes multiple oxide growth operations at different laser operation conditions, for example at different locations on the exterior surface of the metal material. 
     In additional embodiments, operation  1230  comprises forming diffraction features along the exterior of the metal portion which provide a structural color through diffraction of light. In further embodiments, operation  1230  gives a desired metallic color to the marking area. The metallic color may be characterized by a reflectivity as well as a color. In some embodiments, a steel, titanium, or titanium alloy substrate may be given the appearance of a metal such as silver, palladium, platinum, or gold. In further embodiments, a metallic color may be obtaining by limiting the extent of annealing of the metal portion, such as by using a relatively low power and/or a relatively high scan speed. 
     In embodiments, operation  1230  may use a nanosecond laser producing pulses having an effective pulse duration in the nanosecond range. In embodiments, the nanosecond laser is used to form a metal oxide layer. The nanosecond laser may produce a wavelength in the near infrared range. The pulse duration may be from about 2 ns to about 500 ns, the average power may be from about 1 W to about 15 W, and the repetition rate may be from about 100 kHz to about 750 kHz or from about 100 kHz to about 500 kHz. In some embodiments, the laser may be operated in burst mode, with each burst including multiple pulses. In embodiments, the number of pulses in the burst may be from 5 to 25. The scan speed may be from about 100 mm/sec to about 2000 mm/sec or from about 100 mm/sec to about 800 mm/sec. The number of passes may be from 1 to 15 or 2 to 20. The spot size may be from about 10 μm to about 50 μm. The hatch distance may be up to about 50 μm, or from about 10 μm to about 30 μm. In embodiments, the hatch distance may be less than, approximately equal to, or greater than the spot size. 
     In additional embodiments, operation  1230  may use a femtosecond laser producing pulses having an effective pulse duration in the femtosecond range. The femtosecond laser may produce a wavelength in the near infrared range. The pulse duration may be from 200 fs to 800 fs, the average power may be from about 1 W to about 15 W, and the repetition rate may be from about 100 kHz to about 750 kHz. In some embodiments, the laser may be operated in burst mode, with each burst including multiple pulses. In embodiments, the number of pulses in the burst may be from 5 to 25. The scan speed may be from about 800 mm/sec to about 1200 mm/sec or from about 1000 mm/sec to about 1750 mm/sec, the hatch distance up to 50 μm, and the number of passes from 1 to 10. The spot size may be from about 5 μm to about 50 μm. 
       FIGS. 13A, 13B, 13C, and 13D  schematically illustrate three stages in an example process for forming a marking along an exterior surface of an article.  FIG. 13A  shows a device component  1310  of the article prior to any process operations. The device component  1310  comprises a coating  1330  disposed over an exterior surface  1312  of a metal material  1340 . As shown in  FIGS. 13A-13D  the coating  1330  comprises a first layer  1334  and a second layer  1336 . An exterior surface of second layer  1336  forms an exterior surface  1302  of the article. The area over which the marking is to be formed (marking area  1322 ), the first portion  1331  of the coating to be removed, and a second portion  1332  of the coating to remain are also shown. 
       FIG. 13B  shows the device component  1310  of the article partially through the operation of removing the first portion of the coating ( 1331  as shown in  FIG. 13A ) using the first laser (not shown). Recess  1361  has been formed at a periphery of the marking area  1322  through second layer  1336  and a portion of first layer  1334  of the coating  1330 . The recess  1361  therefore can form an outline for the marking area  1322 . The coating  1330  is disposed over an exterior surface  1312  of the metal material  1340  and an exterior surface of second layer  1336  forms an exterior surface  1302  of the article. 
     The operation of removing the first portion of the coating may continue by removing a remainder of the first portion of the coating within the outline defined by recess  1361  and also below recess  1361 . Different laser conditions may be used to form the outline than to remove the remainder of the first portion of the coating. In embodiments, the laser used to form the outline may be operated under conditions which minimize damage to the second layer  1336  in the second portion  1332  of the coating  1330 . For example, the laser used to form the outline may be operated at a lower power and/or at a lower repetition rate as described for the operation  1210  of the process  1200 . 
     As shown in  FIG. 13C , the operation of removing the first portion  1331  of the coating  1330  in the marking area  1322  may creates a recess  1363  extending through the coating  1330  and surrounded by the second portion  1332  of the coating  1330 . As previously discussed with respect to  FIG. 12 , a first laser may be used to remove the first portion  1331  of the coating  1330 . The second portion  1332  of the coating  1330  surrounding the recess  1363  defines a recess wall  1364 . As shown in  FIG. 13D , the recess wall  1364  can be part of the relief feature  1360 . In embodiments, the operation of removing the first portion  1331  of the coating  1330  produces few, if any, cracks in the recess wall  1364 . For example, the operation of removing the first portion  1331  of the coating  1330  may produce a recess wall  1364  which has no cracks visually discernable to the human eye at a normal viewing distance. Therefore, the multilayer coating may not include visible cracks along the recess wall. 
     The operation of removing the first portion  1331  of the coating also creates an exposed metal portion of the substrate  1340  under the recess  1353 . As illustrated in  FIG. 13C , the exposed metal portion may correspond to an exterior surface  1314  of the substrate  1340 . The exterior surface  1314  is not required to be at the same height as the exterior surface  1312  of the metal material  1340  (under the second portion  1332  of the coating). For example, the operation of removing the first portion  1331  of the coating  1330  may cause the exterior surface  1314  to be recessed with respect to the exterior surface  1312 . In some embodiments, the exterior surface  1314  is recessed by 5 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less with respect to the exterior surface  1312 . 
       FIG. 13D  shows the device component  1310  after laser texturing within the marking area  1322  of the article. As an example, modifying the exposed metal portion/exterior surface  1314  of the substrate  1340  creates a recessed marking feature  1366  of the relief feature  1360 . As previously discussed with respect to  FIG. 12 , the exposed metal portion/exterior surface  1314  may be modified using a second laser. The recessed marking feature  1366  may comprise a geometric feature  1372 , such as a groove, formed into the exterior surface  1314  as illustrated in  FIG. 13D . As previously described with respect to  FIG. 12 , the recessed marking feature  1366  may alternately or additionally comprise a metal oxide layer formed along exterior surface  1314 . Additional description of features which are shared or similar to those previously described with respect to any of  FIG. 13A-13C  is omitted to reduce redundancy. 
       FIG. 14  illustrates a flowchart of an example process  1400  for forming a marking along an exterior surface of an article. The process  1400  may be used to form a relief feature having a recessed marking feature. The recessed marking feature may be formed along an exterior surface of an exposed metal portion of a substrate; an oxide layer may be formed along the exterior surface of the exposed metal portion to produce a visual effect. As examples, process  1400  may be used to form the recessed marking features of  FIGS. 6-8 . 
     The operation  1410  of the process  1400  comprises laser ablating the coating in a marking area of the article. The marking area is along an exterior surface of the article defined by an exterior surface of the coating. As an example, operation  1410  comprises removing, using a first laser, a first portion of the coating. For example, the first laser may be a femtosecond laser producing pulses having an effective pulse duration in the femtosecond range. The first laser may produce a wavelength in the ultraviolet range. The first laser may be operated in a vector mode, a raster mode, or a combination thereof. The laser operating conditions may be as previously described for the operation  1210  of the process  1200  and, for brevity, that description is not repeated here. 
     As previously described with respect to the operation  1210  of the process  1200 , the operation  1410  may comprise ablating an outline in a first portion of the coating followed by removing a remainder of the first portion of the coating. Different laser conditions may be used to form the outline than to remove the remainder of the first portion of the coating. For example, the laser conditions may be as described for the operation  1210  of the process  1210  and, for brevity, that description is not repeated here. 
     The operation  1410  of removing the first portion of the coating using the first laser can form a recess extending through the coating and surrounded by a second portion of the coating. The operation of removing the first portion of the coating also can create an exposed metal portion of the substrate under the recess extending through the coating. The operation of removing the first portion of the coating may be similar to that schematically illustrated by  FIGS. 13A, 13B and 13C . 
     The operation  1420  of the process  1400  comprises laser coloring the marking area. In embodiments, the operation  1420  comprises thermally growing a metal oxide layer in the marking area of the article. As an example, the operation  1420  comprises modifying the exposed metal portion, using a second laser, to create a metal oxide layer along an exterior surface of the exposed metal portion. For example, the second laser may be a nanosecond laser producing pulses having an effective pulse duration in the nanosecond range. The laser may produce a wavelength in the near infrared range. In additional embodiments, the second layer may be a femtosecond laser producing pulses having an effective pulse duration in the femtosecond range. The laser conditions may be similar to those described for the operation  1230  of the process  1200  shown in  FIG. 12  and, for brevity, that description is not repeated here. In some embodiments, the operation of thermally growing the oxide layer includes multiple oxide growth operations at different laser operation conditions, for example at different locations on the exterior surface of the metal material. 
     Process  1400  optionally includes an operation of  1430  of laser texturing the laser colored marking area. Laser texturing the laser colored area can comprise ablating a metal oxide or can comprise deeper ablation into the metal material, such as the metal material below the metal oxide. The operation of laser texturing may use a third laser. For example, the third laser may be a femtosecond laser producing pulses having an effective pulse duration in the femtosecond range. The third laser may produce a wavelength in the infrared range. The third laser may be operated in a vector mode, a raster mode, or a combination thereof. The pulse duration may be from 200 fs to 800 fs, the average power may be from about 0.01 W to about 15 W or from about 0.05 W to about 5 W, or from about 1 W to about 15 W. The repetition rate may be from about 10 kHz to about 100 kHz or from about 50 kHz to about 750 kHz. The scan speed may be from about 200 mm/sec to about 1500 mm/sec, the hatch distance from about 5 μm to about 30 μm, and the number of passes from 1 to 10. The spot size may be from 10 μm to 50 μm. In some embodiments, the laser may be operated in burst mode, with each burst including multiple pulses. In embodiments, the number of pulses in the burst may be from 5 to 25. In some embodiments, the average power may be less than that used in the laser coloring operation. 
       FIG. 15  shows a flowchart of an additional process  1500  for making a marking. The process  1500  includes an operation  1510  of laser ablating the coating in a marking area. Process conditions for the operation  1510  may be similar to those of the operation  1210  of the process  1200  shown in  FIG. 12  and, for brevity, that description is not repeated here. 
     The process  1500  further includes an operation  1520  of laser shaping and/or texturing the marking area. As an example, the metal portion may be laser shaped through ablation to form a depression or other geometric shape and then laser textured to polish the laser-formed shape. The process conditions for laser shaping may be similar to those described for forming a geometric shape in the operation  1220  of the process  1200  of  FIG. 12  and, for brevity, that description is not repeated here. The process conditions for laser texturing the marking area may also be similar to those described for the operation  1220  of the process  1200  shown in  FIG. 12  and, for brevity, that description is not repeated here. 
     Process  1500  further includes operation  1530  of laser coloring the marking area. Typically, operation  1530  follows operation  1520 . Process conditions for the operation  1530  may be similar to those described for the operation  1230  of the process  1200  shown in  FIG. 12 . 
     In addition, process  1500  includes operation  1540  of laser ablating and/or texturing the marking area following thermal growth of the metal oxide layer. For example, the operation of laser texturing the marking area may include modifying the metal oxide layer, using a laser, to produce the recessed marking feature of the relief feature. The laser may ablate the metal oxide layer to produce one or more desired thicknesses in the oxide or to produce a geometric feature such as a groove. In embodiments, the laser is a femtosecond laser. The laser conditions may be similar to those described for the operation  1430  of the process  1400  shown in  FIG. 14  and, for brevity, that description is not repeated here. In additional embodiments, operation  1540  is optional. 
       FIG. 16  is a block diagram of example components of an example article or electronic device. The schematic representation depicted in  FIG. 16  may correspond to the article (e.g., an electronic device) depicted in  FIGS. 1A-1C  as described above. However, the article of  FIGS. 1A-1C  need not include all the components shown in  FIG. 16 .  FIG. 16  may also more generally represent other types of electronic devices with a marking, as described herein. Further, the marking techniques described herein may be used to mark a component of the electronic device  1600  including, for example, the device enclosure, housing, cover, or other device component 
     As shown in  FIG. 16 , the electronic device  1600  includes a processor  1604  operably connected with a computer-readable memory  1602 . The processor  1604  may be operatively connected to the memory  1602  component via an electronic bus or bridge. The processor  1604  may be implemented as one or more computer processors or microcontrollers configured to perform operations in response to computer-readable instructions. The processor  1604  may include a central processing unit (CPU) of the device  1600 . Additionally and/or alternatively, the processor  1604  may include other electronic circuitry within the device  1600  including application specific integrated chips (ASIC) and other microcontroller devices. The processor  1604  may be configured to perform functionality described in the examples above. In addition, the processor or other electronic circuitry within the device may be provided on or coupled to a flexible circuit board in order to accommodate folding or bending of the electronic device. 
     The memory  1602  may include a variety of types of non-transitory computer-readable storage media, including, for example, read access memory (RAM), read-only memory (ROM), erasable programmable memory (e.g., EPROM and EEPROM), or flash memory. The memory  1602  is configured to store computer-readable instructions, sensor values, and other persistent software elements 
     The electronic device  1600  may include control circuitry  1606 . The control circuitry  1606  may be implemented in a single control unit and not necessarily as distinct electrical circuit elements. As used herein, “control unit” will be used synonymously with “control circuitry.” The control circuitry  1606  may receive signals from the processor  1604  or from other elements of the electronic device  1600 . 
     As shown in  FIG. 16 , the electronic device  1600  includes a battery  1608  that is configured to provide electrical power to the components of the electronic device  1600 . The battery  1608  may include one or more power storage cells that are linked together to provide an internal supply of electrical power. The battery  1608  may be operatively coupled to power management circuitry that is configured to provide appropriate voltage and power levels for individual components or groups of components within the electronic device  1600 . The battery  1608 , via power management circuitry, may be configured to receive power from an external source, such as an alternating current power outlet. The battery  1608  may store received power so that the electronic device  1600  may operate without connection to an external power source for an extended period of time, which may range from several hours to several days. The battery may be flexible to accommodate bending or flexing of the electronic device. For example, the battery may be mounted to a flexible housing or may be mounted to a flexible printed circuit. In some cases, the battery is formed from flexible anodes and flexible cathode layers and the battery cell is itself flexible. In some cases, individual battery cells are not flexible, but are attached to a flexible substrate or carrier that allows an array of battery cells to bend or fold around a foldable region of the device. 
     In some embodiments, the electronic device  1600  includes one or more input devices  1610 . The input device  1610  is a device that is configured to receive input from a user or the environment. The input device  1610  may include, for example, a push button, a touch-activated button, a touch screen (e.g., a touch-sensitive display or a force-sensitive display), capacitive touch button, dial, crown, or the like. In some embodiments, the input device  1610  may provide a dedicated or primary function, including, for example, a power button, volume buttons, home buttons, scroll wheels, and camera buttons. 
     The device  1600  may also include one or more sensors  1620 , such as a force sensor, a capacitive sensor, an accelerometer, a barometer, a gyroscope, a proximity sensor, a light sensor, or the like. The sensors  1620  may be operably coupled to processing circuitry. In some embodiments, the sensors  1620  may detect deformation and/or changes in configuration of the electronic device and be operably coupled to processing circuitry which controls the display based on the sensor signals. In some implementations, output from the sensors  1620  is used to reconfigure the display output to correspond to an orientation or folded/unfolded configuration or state of the device. Example sensors  1620  for this purpose include accelerometers, gyroscopes, magnetometers, and other similar types of position/orientation sensing devices. In addition, the sensors  1620  may include a microphone, acoustic sensor, light sensor, optical facial recognition sensor, or other types of sensing device. 
     In some embodiments, the electronic device  1600  includes one or more output devices  1612  configured to provide output to a user. The output device may include display  1614  that renders visual information generated by the processor  1604 . The output device may also include one or more speakers to provide audio output. 
     The display  1614  may include a liquid-crystal display (LCD), light-emitting diode, organic light-emitting diode (OLED) display, an active layer organic light emitting diode (AMOLED) display, organic electroluminescent (EL) display, electrophoretic ink display, or the like. If the display  1614  is a liquid-crystal display or an electrophoretic ink display, the display may also include a backlight component that can be controlled to provide variable levels of display brightness. If the display  1614  is an organic light-emitting diode or organic electroluminescent type display, the brightness of the display  1614  may be controlled by modifying the electrical signals that are provided to display elements. In addition, information regarding configuration and/or orientation of the electronic device may be used to control the output of the display as described with respect to input devices  1610 . 
     In embodiments, an electronic device  1600  may include sensors  1620  to provide information regarding configuration and/or orientation of the electronic device in order to control the output of the display. For example, a portion of the display  1614  may be turned off, disabled, or put in a low energy state when all or part of the viewable area of the display  1614  is blocked or substantially obscured. As another example, the display  1614  may be adapted to rotate the display of graphical output based on changes in orientation of the device  1600  (e.g., 90 degrees or 180 degrees) in response to the device  1600  being rotated. 
     The electronic device  1600  may also include a communication port  1616  that is configured to transmit and/or receive signals or electrical communication from an external or separate device. The communication port  1616  may be configured to couple to an external device via a cable, adaptor, or other type of electrical connector. In some embodiments, the communication port  1616  may be used to couple the electronic device to a host computer. 
     The electronic device may also include at least one accessory  1618 , such as a camera, a flash for the camera, or other such device. The camera may be connected to other parts of the electronic device such as the control circuitry. 
     The following discussion applies to the electronic devices described herein to the extent that these devices may be used to obtain personally identifiable information data. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20190628
Publication Date: 20210216
Grant Date: 20210216
Priority Date: 20180703
Inventors: NASHNER, MICHAEL S.
RUSSELL-CLARKE, Peter N.
Assignee: APPLE INC
CPC Classifications: [{"code": "B41M5/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0283", "inventive": true, "first": false, "tree": "[]"}, {"code": "B41M5/24", "inventive": true, "first": true, "tree": "[]"}, {"code": "B44C1/228", "inventive": true, "first": true, "tree": "[]"}, {"code": "B32B3/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/364", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K26/702", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B9/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B3/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "B44C3/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B38/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B3/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B3/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B38/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B9/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "B41M5/24", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 67145646