PATENT DOCUMENT

Publication Number: US-11136672-B2
Application Number: US-201916539944-A
Country: US
Kind Code: B2

Title: Electronic devices having corrosion-resistant coatings

Abstract:
An electronic device such as a wristwatch may include a conductive housing. A corrosion-resistant coating may be deposited on the conductive housing. The coating may include transition layers and an uppermost alloy layer. The transition layers may include a chromium seed layer on the conductive housing and a chromium nitride layer on the chromium seed layer. The uppermost alloy layer may include TiCrCN or other alloys and may provide the coating with desired optical reflection and absorption characteristics. The transition layers may include a minimal number of coating defects, thereby eliminating potential sites at which visible defects could form when exposed to salt water. This may allow the electronic device to exhibit a desired color and to be submerged in salt water without producing undesirable visible defects on the conductive housing structures.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a conductive housing structure; and 
 a coating on the conductive housing structure, the coating comprising:
 a chromium seed layer on the conductive housing structure, 
 a chromium nitride layer on the chromium seed layer, and 
 a TiCrCN layer on the chromium nitride layer. 
 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the TiCrCN layer is an uppermost layer of the coating. 
     
     
       3. The electronic device defined in  claim 1 , further comprising an antismudge layer on the TiCrCN layer. 
     
     
       4. The electronic device defined in  claim 1 , wherein the conductive housing structure comprises stainless steel having an inclusion count less than 75 per 10,000 square microns. 
     
     
       5. The electronic device defined in  claim 1 , wherein the electronic device has opposing front and rear faces, the electronic device further comprising:
 a display at the front face, wherein the conductive housing structure comprises a conductive wall at the rear face. 
 
     
     
       6. The electronic device defined in  claim 1 , wherein the coating has a total thickness between 1.0 micron and 2.0 microns. 
     
     
       7. The electronic device defined in  claim 6 , wherein the TiCrCN layer has a first thickness, the chromium nitride layer has a second thickness greater than the first thickness, and the chromium seed layer has a third thickness less than the first thickness. 
     
     
       8. The electronic device defined in  claim 1 , wherein the TiCrCN layer has a molar % of nitrogen between 25% and 35%, a molar % of carbon between 10% and 25%, and a molar % of chromium between 1% and 10%. 
     
     
       9. An electronic device comprising:
 a display; 
 a conductive housing wall; and 
 a coating on the conductive housing wall that configures the conductive housing wall to exhibit a given color, the coating comprising:
 a chromium seed layer on the conductive housing wall, 
 a transition layer on the chromium seed layer, the transition layer comprising chromium, and 
 an uppermost alloy layer comprising nitrogen. 
 
 
     
     
       10. The electronic device defined in  claim 9 , wherein the transition layer comprises a chromium nitride layer. 
     
     
       11. The electronic device defined in  claim 10 , wherein the uppermost alloy layer comprises a TiCrCN layer. 
     
     
       12. The electronic device defined in  claim 10 , wherein the uppermost alloy layer comprises a CrCN layer. 
     
     
       13. The electronic device defined in  claim 10 , wherein the uppermost alloy layer comprises a TiAlN layer. 
     
     
       14. The electronic device defined in  claim 10 , wherein the uppermost alloy layer comprises a TiAlCrN layer. 
     
     
       15. The electronic device defined in  claim 10 , wherein the uppermost alloy layer comprises a TiCN layer and the coating further comprises a titanium layer interposed between the chromium nitride layer and the TiCN layer. 
     
     
       16. The electronic device defined in  claim 9 , wherein the transition layer comprises a CrSi layer, the uppermost alloy layer comprises a CrSiCN layer, and the coating further comprises a CrSiN layer interposed between the CrSi layer and the CrSiCN layer. 
     
     
       17. The electronic device defined in  claim 9 , wherein the transition layer comprises a CrC layer and the uppermost alloy layer comprises a CrCN layer. 
     
     
       18. An electronic device, comprising:
 a stainless steel housing structure; 
 a corrosion-resistant coating on the stainless steel housing structure, wherein the corrosion-resistant coating comprises a chromium nitride layer and an uppermost coloring layer; and 
 an oleophobic coating on the corrosion-resistant coating.

Description:
This application claims the benefit of provisional patent application No. 62/725,153, filed Aug. 30, 2018, and provisional patent application No. 62/729,911, filed Sep. 11, 2018, which are hereby incorporated by reference herein in their entireties. 
    
    
     FIELD 
     This relates generally to coatings for electronic device structures and, more particularly, to corrosion-resistant coatings for conductive electronic device housings. 
     BACKGROUND 
     Electronic devices such as cellular telephones, computers, watches, and other devices contain housings that include conductive housing structures. The conductive housing structures are provided with a coating that reflects particular wavelengths of light so that the conductive housing structures exhibit a desired color. 
     It can be difficult to provide coatings that are resistant to corrosion and other environmental factors. If care is not taken, these coatings can be prone to corrosion-related damage. Corrosion-related damage can create unsightly visible defects in the coating and can undesirably deteriorate the color of the conductive housing structures. 
     SUMMARY 
     An electronic device such as a wristwatch may include conductive structures. The conductive structures may include conductive housing structures. A display may be mounted to the conductive housing structures. 
     A corrosion-resistant coating may be formed on the conductive housing structures. The corrosion-resistant coating may include transition layers and an uppermost alloy layer. The transition layers may include a chromium seed layer on the conductive housing structures and an additional layer on the chromium seed layer. The additional layer may also include chromium and may be, for example, a chromium nitride layer. 
     The uppermost alloy layer may include TiCrCN or other alloys and may provide the coating with desired optical reflection and absorption characteristics. This may configure the coating and thus the underlying conductive housing structures to exhibit a desired color. The transition layers may be deposited using physical vapor deposition techniques. The transition layers may include a minimal number of coating defects, thereby eliminating potential sites at which visible defects could form when exposed to salt water. This may allow the electronic device to exhibit a desired color and to be submerged in salt water without producing undesirable visible defects on the conductive housing structures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device of the type that may be provided with conductive housing structures with corrosion-resistant coatings in accordance with an embodiment. 
         FIG. 2  is cross-sectional side view of an illustrative electronic device having conductive housing structures that may be provided with a corrosion-resistant coating in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view showing how an illustrative corrosion-resistant coating may include transition layers (e.g., including metallic adhesion and seed layers) and a top coloring layer over a substrate such as a conductive housing structure in accordance with an embodiment. 
         FIG. 4  is a rear perspective view of an illustrative electronic device having corrosion-related damage on conductive housing structures in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of potential corrosion initiation sites based on material-related defects that may arise in non-corrosion-resistant coatings in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative corrosion-resistant coating having chromium and chromium nitride transition layers in accordance with an embodiment. 
         FIG. 7  is a plot of illustrative nitrogen and carbon content in a top color layer of a corrosion-resistant coating of the type shown in  FIG. 6  in accordance with an embodiment. 
         FIGS. 8-13  are cross-sectional side views of illustrative corrosion-resistant coatings of different colors having chromium nitride-based transition layers in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices and other items may be provided with conductive structures. Coatings may be formed on the conductive structures to reflect particular wavelengths of light so that the conductive structures exhibit a desired color. The coatings may be provided with layers that make the coatings corrosion-resistant (e.g., so that the visible corrosion defects do not form on the coating or the underlying conductive structures in the presence of salt water). 
     The corrosion-resistant coating may include transition layers on a conductive substrate. The transition layers may include a seed/adhesion layer (e.g., a metal layer that affixes the coating system to the metal substrate and forms the basis for the nitride-based color/functional component layers). The transition layers may, for example, include a chromium seed layer and other transition layers such as a chromium nitride layer. The transition layers may be deposited using physical vapor deposition techniques and may include relatively few coating defects, thereby eliminating potential sites at which visible defects could form when exposed to salt water. 
     The coating may include an uppermost coloring layer over the transition layers that is formed from a metal alloy selected to provide the coating with a desired color (e.g., a metallic color such as a rose gold color). In this way, the coating may provide the substrate with a desired color while also making the substrate resistant to corrosion after exposure to salt water. Illustrative configurations in which corrosion-resistant coatings are provided on conductive housing structures for electronic devices may sometimes be described herein as an example. In general, however, corrosion-resistant coatings may be formed on any suitable conductive structures. 
     An illustrative electronic device of the type that may be provided with conductive housing structures and corrosion-resistant coatings is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device (e.g., a watch with a wrist strap), a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a wristwatch (e.g., a smart watch). Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14 . Display  14  may be mounted in a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). Housing  12  may have metal sidewalls or sidewalls formed from other materials. Examples of metal materials that may be used for forming housing  12  include stainless steel, aluminum, silver, gold, metal alloys, or any other desired conductive material. 
     Display  14  may be formed at (e.g., mounted on) the front side (face) of device  10 . Housing  12  may have a rear housing wall on the rear side (face) of device  10  that opposes the front face of device  10 . Conductive housing sidewalls in housing  12  may surround the periphery of device  10 . The rear housing wall of housing  12  may be formed from conductive materials and/or dielectric materials. 
     The rear housing wall of housing  12  and/or display  14  may extend across some or all of the length (e.g., parallel to the X-axis of  FIG. 1 ) and width (e.g., parallel to the Y-axis) of device  10 . Conductive sidewalls of housing  12  may extend across some or all of the height of device  10  (e.g., parallel to Z-axis). 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode (OLED) display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. 
     Display  14  may be protected using a display cover layer. The display cover layer may be formed from a transparent material such as glass, plastic, sapphire or other crystalline dielectric materials, ceramic, or other clear materials. The display cover layer may extend across substantially all of the length and width of device  10 , for example. 
     Device  10  may include buttons such as button  18 . There may be any suitable number of buttons in device  10  (e.g., a single button, more than one button, two or more buttons, five or more buttons, etc. Buttons may be located in openings in housing  12  or in an opening in display  14  (as examples). Buttons may be rotary buttons, sliding buttons, buttons that are actuated by pressing on a movable button member, etc. Button members for buttons such as button  18  may be formed from metal, glass, plastic, or other materials. Button  18  may sometimes be referred to as a crown in scenarios where device  10  is a wristwatch device. 
     Device  10  may, if desired, be coupled to a strap such as strap  16 . Strap  16  may be used to hold device  10  against a user&#39;s wrist (as an example). Strap  16  may sometimes be referred to herein as wrist strap  16 . In the example of  FIG. 1 , wrist strap  16  is connected to opposing sides of device  10 . Conductive sidewalls of housing  12  may include attachment structures for securing wrist strap  16  to housing  12  (e.g., lugs or other attachment mechanisms that configure housing  12  to receive wrist strap  16 ). Configurations that do not include straps may also be used for device  10 . 
     A cross-sectional side view of device  10  in an illustrative configuration in which display  14  has a display cover layer is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may have one or more display layers that form pixel array  22 . During operation, pixel array  22  forms images for a user in an active area of display  14 . Display  14  may also have inactive areas (e.g., areas along the border of pixel array  22 ) that are free of pixels and that do not produce images. Display cover layer  20  of  FIG. 2  overlaps pixel array  22  in the active area and overlaps electrical components in device  10 . 
     Display cover layer  20  may be formed from a transparent material such as glass, plastic, ceramic, or crystalline materials such as sapphire. Illustrative configurations in which a display cover layer and other transparent members in device  10  (e.g., windows for cameras and other light-based devices that are formed in openings in housing  12 ) are formed from a hard transparent crystalline material such as sapphire (sometimes referred to as corundum or crystalline aluminum oxide) may sometimes be described herein as an example. Sapphire makes a satisfactory material for display cover layers and windows due to its hardness (9 Mohs). In general, however, these transparent members may be formed from any suitable material. 
     Display cover layer  20  for display  14  may planar or curved and may have a rectangular outline, a circular outline, or outlines of other shapes. If desired, openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button, a speaker port, or other component. Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, or to form audio ports (e.g., openings for speakers and/or microphones). 
     Conductive structures in device  10  such as conductive portions of housing  12  (e.g., at the exterior of device  10 ) may be provided with a coating that reflects certain wavelengths of light so that housing  12  exhibits a desired aesthetic appearance (e.g., a desired color, reflectivity, etc.). If care is not taken, these coatings and the underlying conductive portions of housing  12  may be susceptible to corrosion when device  10  comes into contact with water. Corrosion may be particularly high in the presence of salt water. In scenarios where device  10  is a wristwatch device, device  10  may frequently come into contact with fresh water or salt water (e.g., when the user is swimming in the ocean, swimming in a lake, swimming in a pool, in the shower, in the rain, sweating during exercise, etc.). It may therefore be desirable to be able to provide device  10  with coatings that both provide housing  12  with desired reflective properties (e.g., colors) while also being resistant to corrosion, particularly corrosion from contact with salt water. Such coatings may sometimes be referred to herein as corrosion-resistant coatings. 
     An illustrative corrosion-resistant coating for conductive structures in device  10  such as conductive portions of housing  12  is shown in  FIG. 3 . As shown in  FIG. 3 , corrosion-resistant coating  24  may be formed on substrate  26 . The layers of corrosion-resistant coating  24  may be deposited using any suitable deposition techniques. Examples of techniques that may be used for depositing layers in coating  24  include physical vapor deposition (e.g., evaporation and/or sputtering), cathodic arc deposition, chemical vapor deposition, ion plating, laser ablation, etc. 
     Substrate  26  may be a conductive structure in device  10  such as a conductive portion of housing  12  ( FIGS. 1 and 2 ). Substrate  26  may be thicker than corrosion-resistant coating  24 . The thickness of substrate  26  may be 0.1 mm to 5 mm, more than 0.3 mm, more than 0.5 mm, between 5 mm and 20 mm, less than 5 mm, less than 2 mm, less than 1.5 mm, or less than 1 mm (as examples). Substrate  26  may include stainless steel, aluminum, titanium, or other metals/alloys. Substrate  26  may include a relatively low number of inclusions to minimize defect initiation sites when coating  24  is deposited over substrate  26 . 
     As shown in  FIG. 3 , coating  24  may include transition layers  28  on substrate  26  and uppermost (top) coloring layer  30  on transition layers  28 . The compositions of top coloring layer  30  and/or one or more of transition layers  28  may configure coating  24  to absorb and reflect light at selected wavelengths to impart coating  24  and substrate  26  with a desired color and reflectivity. Transition layers  28  may include a seed layer that couples substrate  26  to the remaining transition layers  28 . 
     To help prevent smudging on the outermost surface of coating  24 , the outer surface of coating  24  (e.g., the outer surface of top coloring layer  30 ) may be provided with an antismudge layer such oleophobic layer  32 . Layer  32  may be formed from a polymer such as a fluoropolymer or other material that resists smudging. Antismudge layer  32  may be relatively thin (e.g., 7 nm, less than 10 nm, 3-8 nm, more than 2 nm, etc.). 
     Transition layers  28  may include chromium and/or chromium nitride layers that exhibit relatively few coating defects upon deposition and that are thereby resistant to corrosion from the presence of water (e.g., salt water). Forming transition layers  28  using chromium and chromium nitride may allow coating  24  to exhibit lower defect density relative to scenarios where titanium and/or titanium nitride layers are used.  FIG. 4  is a rear perspective view of device  10  in scenarios where a coating that does not include transition layers  28  of  FIG. 3  is provided over housing  12  (e.g., a coating having titanium and/or titanium nitride transition layers). 
     As shown in  FIG. 4 , this type of coating would subject conductive portions of housing  12  to corrosion in the presence of salt water. The corrosion generates visible defects  34  on the surface of housing  12 . Visible defects  34  include discoloration of housing  12  and/or visible pitting in housing  12 , as examples. Visible defects  34  may be formed at locations (sites) where there are coating defects in the coating on housing  12 . 
     All coatings have inherent defects, whether from the coating process or the coating&#39;s inability to cover substrate defects (e.g., inclusions, etc.).  FIG. 5  is a cross-sectional side view of different coating defects  35  that may be present on housing  12  and that may lead to visible defects  34  of  FIG. 4 . As shown in  FIG. 5 , a coating  24 ′ (e.g., a coating without chromium/chromium nitride transition layers  28  of  FIG. 3  such as a coating having titanium/titanium nitride transition layers) may be provided over substrate  26  (e.g., housing  12  of  FIG. 4 ). Coating  24 ′ may include coating defects  35  such as pitting  35 A (i.e., pitting that extends through coating  24 ′ and into substrate  26 ) and pitting  35 B (i.e., pitting that extends through coating  24 ′ but not into substrate  26 ). Coating defects  35  can also include protrusion defects  35 C generated at cracks  36  in coating  24 ′ and boundary defects  35 D formed at grain boundaries  37  in coating  24 ′. 
     Coating defects such as coating defects  35 A,  35 B,  35 C, and  35 D may lead to visible defects  34  of  FIG. 4  when exposed to salt water. For example, electrolytes in the salt water may galvanically couple the coating to substrate  26  at the location of defects  35 A,  35 B,  35 C, or  35 D. This may produce oxidation such as rust deposits on the outer surface of coating  24 ′ and/or on exposed portions of substrate  26 . These rust deposits alter the color and appearance of the coating and substrate, leading to visible defects  34  of  FIG. 4 . 
     Transition layers  28  of  FIG. 3  (e.g., transition layers that include chromium and chromium nitride) may have a lower defect density than other transition layers such as titanium and titanium nitride transition layers (e.g., corrosion-resistant coating  24  of  FIG. 3  will exhibit fewer defects such as defects  35  of  FIG. 5  than titanium and titanium nitride transition layers). Because transition layers  28  have relatively few (e.g., zero) defects  35 , housing  12  may be provided with a desired color (e.g., by corrosion-resistant coating  24 ) without the generation of visible defects  34  ( FIG. 4 ) after exposure to salt water. 
       FIG. 6  is a cross-sectional diagram showing one example of layers that may be included in corrosion-resistant coating  24 . Coating  24  reduces or minimizes the total number of defects by providing a low inclusion-containing substrate with a coating system that is tailored to have fewer inherent defects (e.g., relative to coating  24 ′ of  FIG. 5 ). As shown in  FIG. 6 , transition layers  28  in coating  24  may include a chromium seed layer such as chromium layer  38  and a chromium nitride transition layer such as chromium nitride (CrN) layer  40 . Chromium layer  38  may be coated over substrate  26 . Chromium nitride layer  40  may be coated over chromium layer  38 . Top (uppermost) coloring layer  30  may include an alloy layer such as titanium-chromium-carbon-nitrogen (TiCrCN) layer  41  coated over chromium nitride layer  40  (e.g., an alloy layer that includes titanium, chromium, carbon, and nitrogen). Optional antismudge layer  32  may be provided over TiCrCN layer  41  if desired. 
     Antismudge layer  32  has thickness T 1 . TiCrCN layer  41  has thickness T 2 . Chromium nitride layer  40  has thickness T 3 . Chromium layer  38  has thickness T 4 . Thickness T 1  may be less than each of thicknesses T 2 , T 3 , and T 4 . Each of thicknesses T 1 , T 2 , T 3 , and T 4  (and the total thickness of coating  24 ) may be less than the thickness of substrate  26 . The total thickness of coating  24  may be, for example, between 1.0 micron and 2.0 microns, between 1.2 microns and 1.8 microns, between 0.5 microns and 2.5 microns, less than 0.5 microns, or greater than 2.5 microns. In the example of  FIG. 6 , thickness T 4  is less than thickness T 2  and thickness T 2  is less than thickness T 3 . This is merely illustrative and, in general, thicknesses T 2 , T 3 , and T 4  may have any desired values (e.g., other relative thicknesses may be used if desired). 
     Chromium nitride layer  40  and chromium layer  38  may have a low defect density after deposition (e.g., physical vapor deposition). This may serve to mitigate visible defects (e.g., visible defects  34  of  FIG. 4 ) on substrate  26  after exposure to salt water. If desired, chromium nitride layer  40  and chromium layer  38  may help to adhere top TiCrCN layer  41  to substrate  26  and/or may contribute to the color profile of coating  24 . Coating  24  may exhibit a hardness of greater than 1500 nHVN, as an example. 
     TiCrCN layer  41  may provide coating  24  with desired light reflecting properties so that coating  24  reflects desired wavelengths of light. This may impart coating  24  and thus substrate  26  (e.g., housing  12  of  FIGS. 1 and 2 ) with desired aesthetic properties such as a desired color, reflectivity, luster, etc. As an example, layer  41  may provide coating  24  and housing  12  with a light red or red-gold color (e.g., a rose gold or blush gold color). The composition of TiCrCN layer  41  may be selected to adjust the light absorption and reflection properties of coating  24 . 
       FIG. 7  is an exemplary plot of the chemical composition of TiCrCN layer  41 . The X-axis of  FIG. 7  plots the molar % of nitrogen in layer  41  whereas the Y-axis plots the molar % of carbon in layer  41 . Layer  41  may have a molar % of nitrogen between limits X 1  and X 2  and a molar % of carbon between limits Y 1  and Y 2 . Limit X 1  may be, for example, 30%, 35%, 20%, 25%, between 20% and 40%, between 25% and 35%, between 27% and 33%, or other values. Limit X 2  may be, for example, 40%, 45%, 30%, 35%, between 30% and 50%, between 35% and 45%, between 37% and 43%, or other values greater than limit X 1 . Limit Y 1  may be, for example, 10%, 15%, between 10% and 15% (e.g., 13%, 14%, etc.), between 5% and 20%, or other values. Limit Y 2  may be, for example, 20%, 25%, between 20% and 25% (e.g., 22%, 23%, etc.), between 15% and 25%, or other values greater than limit Y 1 . In general, the sum of the molar % of nitrogen and the molar % of carbon in layer  41  may be between 45% and 55%, between 44% and 54%, between 40% and 60%, etc. By bounding the chemical composition in this way, coating  24  may provide housing  12  with a desired color and other aesthetic characteristics. 
     The example of  FIG. 7  is merely illustrative. The plot of  FIG. 7  may include an additional dimension (not shown) plotting the molar % of chromium. As an example, layer  41  may include between 2% and 10%, between 1% and 11%, between 3% and 9%, between 4% and 8%, or other amounts of chromium. Coating  24  may be provided with other reflective characteristics to provide housing  12  with other colors. ZrCrCN or TiZrCrCN may be used to form layer  41  (e.g., while providing coating  24  with similar color characteristics to TiCrCN). 
       FIGS. 8-13  show examples of different layers that may be used to form coating  24  with different reflective characteristics (e.g., colors). Optional antismudge layer  32  is omitted from  FIGS. 8-13  for the sake of clarity. 
     As shown in  FIG. 8 , transition layers  28  in coating  24  may include a chromium seed layer such as chromium layer  48  on substrate  26 , a chromium-silicon (CrSi) transition layer  46  on chromium layer  48 , and a chromium-silicon-nitrogen (CrSiN) transition layer  44  on CrSi layer  46 . Top coloring layer  30  may include a chromium-silicon-carbon-nitrogen (CrSiCN) layer  42  (e.g., an alloy layer including chromium, silicon, carbon, and nitrogen) on CrSiN layer  44 . Coating  24  of  FIG. 8  may, for example, provide housing  12  with a corrosion-resistant grey color. 
     As shown in  FIG. 9 , transition layers  28  in coating  24  may include a chromium seed layer such as chromium layer  54  on substrate  26  and a chromium-carbon (CrC) transition layer  52  on chromium layer  54 . Top coloring layer  30  may include a chromium-carbon-nitrogen (CrCN) layer  50  (e.g., an alloy layer including chromium, carbon, and nitrogen) on CrC layer  52 . Coating  24  of  FIG. 9  may, for example, provide housing  12  with a corrosion-resistant black color. 
     As shown in  FIG. 10 , transition layers  28  in coating  24  may include a chromium seed layer such as chromium layer  60  on substrate  26  and a chromium nitride transition layer  58  on chromium layer  60 . Top coloring layer  30  may include chromium-carbon-nitrogen (CrCN) layer  56  on chromium nitride layer  58 . Coating  24  of  FIG. 10  may, for example, provide housing  12  with a corrosion-resistant bronze color. 
     As shown in  FIG. 11 , transition layers  28  in coating  24  may include a chromium seed layer such as chromium layer  66  on substrate  26  and a chromium nitride transition layer  64  on chromium layer  66 . Top coloring layer  30  may include titanium-aluminum-nitrogen (TiAlN) layer  62  (e.g., an alloy layer including titanium, aluminum, and nitrogen) on chromium nitride layer  64 . Coating  24  of  FIG. 11  may, for example, provide housing  12  with a corrosion-resistant blue color. 
     As shown in  FIG. 12 , transition layers  28  in coating  24  may include a chromium seed layer such as chromium layer  72  on substrate  26  and a chromium nitride transition layer  70  on chromium layer  72 . Top coloring layer  30  may include titanium-aluminum-chromium-nitrogen (TiAlCrN) layer  68  (e.g., an alloy layer including titanium, aluminum, chromium, and nitrogen) on chromium nitride layer  70 . Coating  24  of  FIG. 12  may, for example, provide housing  12  with a corrosion-resistant green color. 
     As shown in  FIG. 13 , transition layers  28  in coating  24  may include a chromium seed layer such as chromium layer  80  on substrate  26 , a chromium nitride transition layer  78  on chromium layer  80 , and a titanium layer  76  on chromium nitride transition layer  78 . Top coloring layer  30  may include titanium-carbon-nitrogen (TiCN) layer  74  (e.g., an alloy layer including titanium, carbon, and nitrogen) on titanium layer  76 . Coating  24  of  FIG. 13  may, for example, provide housing  12  with a brick red color. 
     The examples of  FIGS. 6-13  are merely illustrative. In general, coating  24  may be provided with any desired layers to provide housing  12  with any desired optically reflective properties (e.g., colors). Chromium-including transition layers  28  may minimize coating defects in coating  24  to thereby mitigate visual defects in coating  24  and housing  12  after exposure to salt water. In some suitable arrangements, layer  30  of coating  24  may be a ZrCrCN or TiZrCrCN layer. If desired, zirconium (Zr) may be used to replace titanium (Ti) in any of the layers of coating  24  described in connection with  FIGS. 6-13 . Substrate  26  may include low-inclusion stainless steel in one example (e.g., SUS 316Li or other stainless steels having an inclusion count less than 75, 50, 20, or 15 per 10,000 square microns or other area). 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20190813
Publication Date: 20211005
Grant Date: 20211005
Priority Date: 20180830
Inventors: TRYON, BRIAN S.
YANG, Isabel
MINTZ, TODD
LI, JEREMY
GABLE, BRIAN
BAO, LIJIE
CHEN, YI
PREST, CHRISTOPHER D.
YURKO, JAMES
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K5/0217", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04B37/226", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04B37/22", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/321", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/0664", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/0641", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/024", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/0015", "inventive": true, "first": true, "tree": "[]"}, {"code": "C23C28/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/34", "inventive": true, "first": true, "tree": "[]"}, {"code": "C23C28/34", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/321", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04B37/226", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/322", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0243", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/0641", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/321", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/34", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04B37/22", "inventive": true, "first": true, "tree": "[]"}, {"code": "C23C14/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/0664", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/322", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/024", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C14/0015", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04B37/226", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/321", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C28/34", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 69642107