PATENT DOCUMENT

Publication Number: US-10590559-B2
Application Number: US-201514835541-A
Country: US
Kind Code: B2

Title: Anodizing and pre-anodizing processes based on incoming laser textured part

Abstract:
Substrates having laser textured surfaces and methods for forming the same are described. The methods involve using a laser to form three-dimensional features on a surface of the substrate. The laser three-dimensional features can be designed to interact with incident light to create unique visual effects. In some embodiments, the substrate is further treated with a pre-anodizing process and an anodizing process to form a protective metal oxide coating. In some cases, the type of pre-anodizing and anodizing process are chosen based on the geometry of the three-dimensional features and to enhance the visual effects.

Claims:
What is claimed is: 
     
       1. A method of forming a housing for a portable electronic device, the method comprising:
 forming surface features on a planar surface of a metal substrate by using a laser, wherein the surface features are arranged according to a regular and repeating pattern, wherein at least one of the surface features includes a cavity defined by walls that (i) extend from the planar surface and into the metal substrate to a depth of at least 10 micrometers, and (ii) include a first reflective micro-feature and a second reflective micro-feature; and 
 forming an anodized layer from the metal substrate such that the anodized layer overlays the surface features, wherein the first and second reflective micro-features are oriented at first and second angles, respectively, relative to an external surface of the anodized layer. 
 
     
     
       2. The method of  claim 1 , wherein using the laser to form the surface features comprises:
 melting a portion of the metal substrate; and 
 resolidifying the melted portion of the metal substrate. 
 
     
     
       3. The method of  claim 2 , wherein the laser ablates the portion of the metal substrate. 
     
     
       4. The method of  claim 2 , wherein the walls are formed of resolidifed metal. 
     
     
       5. The method of  claim 1 , wherein the housing is characterized as having a uniform thickness, and a thickness of the metal substrate and a thickness of the anodized layer contribute to the uniform thickness. 
     
     
       6. The method of  claim 1 , wherein the surface features have widths between 100 micrometers to 1 millimeter. 
     
     
       7. A housing for a portable electronic device, the housing comprising:
 a metal substrate having a planar external surface including a repeated and regular pattern of surface features, wherein at least one of the surface features includes a cavity defined by walls that (i) extend from the planar external surface and into the metal substrate to a depth of at least 10 micrometers, and (ii) include a first reflective micro-feature and a second reflective micro-feature; and 
 an anodized layer overlaying the surface features, wherein the first and second reflective micro-features are oriented relative to an external surface of the anodized layer at a first angle and a second angle different than the first angle. 
 
     
     
       8. The housing of  claim 7 , wherein the housing is characterized as having a uniform thickness, and a thickness of the metal substrate and a thickness of the anodized layer contribute to the uniform thickness. 
     
     
       9. The housing of  claim 7 , wherein each of the surface features has a width between 100 micrometers to 1 millimeter. 
     
     
       10. The housing of  claim 7 , wherein the first and second reflective micro-features are included on one of the walls. 
     
     
       11. The housing of  claim 7 , wherein the anodized layer is transparent to visible light that is incident at the external surface of the anodized layer so that the reflective first and second micro-features are viewable through the external surface of the anodized layer. 
     
     
       12. The housing of  claim 7 , wherein portions of the planar external surface of the metal substrate are parallel to the external surface of the anodized layer. 
     
     
       13. The housing of  claim 7 , wherein the anodized layer is characterized as having a shape that is capable of focusing visible light towards the first and second reflective micro-features so as to impart the metal substrate with a sparkling appearance. 
     
     
       14. The housing of  claim 7 , wherein the repeated and regular pattern of surface features is formed by ablating the planar external surface of the metal substrate with a laser. 
     
     
       15. The housing of  claim 7 , wherein visible light that passes through the anodized layer is reflected by the first and second reflective micro-features at varying angles. 
     
     
       16. A housing for a portable electronic device, the housing comprising:
 a metal substrate including a planar surface having a regular and repeating pattern of reflective features, wherein at least one of the reflective features includes a cavity defined by walls that (i) extend from the planar surface and into the metal substrate to a depth of at least 10 micrometers, and (ii) include a first reflective micro-feature and a second reflective micro-feature; and 
 an anodized layer overlaying the reflective features, wherein the first and second reflective micro-features are oriented at first and second different angles, respectively, relative to an external surface of the anodized layer. 
 
     
     
       17. The housing of  claim 16 , wherein the external surface of the anodized layer is parallel to portions of the planar surface of the metal substrate. 
     
     
       18. The housing of  claim 17 , wherein the housing is characterized as having a uniform thickness, and a thickness of the metal substrate and a thickness of the anodized layer contribute to the uniform thickness. 
     
     
       19. The housing of  claim 16 , wherein each of the surface features have a width between 100 micrometers to 1 millimeter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 62/133,240, entitled “ANODIZING AND PRE-ANODIZING PROCESSES BASED ON INCOMING LASER TEXTURED PART” filed Mar. 13, 2015, the content of which is incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD 
     This disclosure relates to systems and methods for forming aesthetic designs on substrate surfaces. In particular, laser texturing, pre-anodizing and anodizing processes are described. 
     BACKGROUND 
     Abrasive blasting operations are often used to create a roughened appearance and texture on surfaces of parts. Abrasive blasting involves forcibly propelling abrasive material against a part until its surface attains a desired texture. The abrasive material, often referred to as blasting media, is typically made of mineral particles, such as silica, alumina or zirconia particles. When the particles strike the surface of the part, the particles leave multiple craters on the surface and a final rugged landscape on the part. 
     Despite the usefulness of blasting for creating textured surfaces, blasting techniques have limitations. For example, controlling the type of texture can only be done in a global sense. In particular, the size of the particles of the blasting media dictates the size of the craters and the force at which the blasting media is propelled against the surface dictates the depth at which the craters are indented within the part. Thus, controlling media particle size and media pressure can be used to determine a final textured surface design. However, the size and depth of each crater cannot be individually controlled. In addition, blasting adds internal stress to the part since blasting involves impinging particles at high energy against the part. If the part is thin, the stresses imparted from the blasting process can deform the part. This is because blasting can impart a compressive stress to the surface of the material by the same mechanism as shot peening. 
     SUMMARY 
     This paper describes various embodiments that relate to laser textured surfaces and methods for forming and treating the same, including anodizing and anodizing pre-treatments. The methods can be used to form decorative surfaces on consumer products, such as electronic devices and accessories. 
     According to one embodiment, a method of forming on a surface, a metal oxide layer having a textured appearance is described. The method involves forming a texture on the surface using a laser beam. The texture includes three-dimensional features. The method also includes modifying an appearance of the texture by increasing or decreasing a light reflectivity of the three-dimensional features. The method further includes forming the metal oxide layer on the textured surface. A thickness and a transparency of the metal oxide layer is chosen based on geometries of the texture. 
     According to another embodiment, a method of forming a decorative design on a surface of a substrate is described. The method includes forming a design on the surface using a laser beam directed at the surface. The design includes light reflective facets. The method also involves increasing light reflective properties of the facets. The method further includes converting a portion of the substrate to a metal oxide layer. The metal oxide layer is sufficiently transparent such that at least some light incident an exterior surface of the metal oxide layer shines through the metal oxide layer and reflects off the light reflective facets. 
     According to a further embodiment, a part having a textured surface is described. The textured surface includes multiple three-dimensional features arranged on the surface as a design. The textured surface also includes a metal oxide layer positioned over the design. The metal oxide layer is substantially transparent to visible light and having an external surface. The multiple three-dimensional features are shaped and sized and spaced a predetermined distance apart from one another to alter the way light incident the external surface is reflected off the multiple three-dimensional features. 
     These and other embodiments will be described in detail below. 
    
    
     
       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 structural elements. 
         FIG. 1  shows perspective views of devices having surfaces that can be textured, in accordance with some embodiments. 
         FIG. 2  shows a cross section view of a substrate undergoing a blasting operation. 
         FIGS. 3A and 3B  show plan view and cross section view of a substrate with laser formed features, in accordance with some embodiments. 
         FIGS. 4A-4D  show cross section views of showing the substrate of  FIGS. 3A and 3B  undergoing a multiple pass laser operation, in accordance with some embodiments. 
         FIGS. 5A-5C  shows the substrate of  FIGS. 3A, 3B and 4A-4D  after surface treatment and anodizing processes, in accordance with some embodiments. 
         FIGS. 6A-6D  show cross section views and a plan view of a substrate that includes faceted features, in accordance with some embodiments. 
         FIGS. 7A-7C  show cross section views of a substrate having light diffracting features, in accordance with some embodiments. 
         FIGS. 8A-8E  show cross section views of substrates having different laser-formed features, in accordance with some embodiments. 
         FIGS. 9A-9C  show plan views of substrates having different laser-formed designs, in accordance with some embodiments. 
         FIG. 10  shows a perspective view of a substrate with a flat surface, curved corners and curved edges that can be laser treated to provide unique visual effects, in accordance with some embodiments. 
         FIGS. 11A-11C  show cross section views and a plan view of a substrate undergoing a laser polishing process, in accordance with some embodiments. 
         FIGS. 12A-12C  show cross section views and a plan view of a substrate undergoing an alternative laser polishing process, in accordance with some embodiments. 
         FIG. 13  shows a flowchart indicating a laser texturing and anodizing process, in accordance with some embodiments. 
     
    
    
     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 embodiment. To the contrary, they are intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments. 
     Described herein are methods relate to creating a predetermined pattern, design or visual effect on a surface of a substrate. The methods involve forming three-dimensional features on the surface of the substrate using a laser texturing process. In some embodiments, the substrate is further treated with a pre-anodizing process and an anodizing process to form a protective metal oxide coating on the substrate. In some cases, the type of pre-anodizing and/or anodizing process is chosen based on the surface geometry of the laser textured surface. 
     The laser texturing processes described herein can be used in place of or in addition to traditional blasting process. Laser texturing techniques provide fine control with regard to the size and shape of the features formed on the substrate, providing a distinct advantage over texturing a surface using only a blasting process. In addition, laser texturing can reduce the amount of compressive stress experienced by the part compared to a blasting process. In some embodiments, the laser formed features are specifically designed to interact with incoming light to produce a unique and aesthetically pleasing appearance. For example, the features can design with geometries that increase reflectance of light or cause light interference effects. Likewise, a pre-anodizing and/or anodizing process can be tailored to enhance these light interactions or create different light interactions on the part. 
     Methods described herein are well suited for providing aesthetically appealing patterns and designs on surfaces of consumer products. For example, the methods described herein can be used to form aesthetically appealing housing or enclosures for portable electronic devices, desktop computers, mobile electronic devices and electronic device accessories, such as those manufactured by Apple Inc., based in Cupertino, Calif. 
     These and other embodiments are discussed below with reference to  FIGS. 1-13 . 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. 
     The methods described herein can be used to form aesthetically appealing surface designs and textures on surface of parts, such as consumer products. Lasers have the ability to not only provide aesthetically pleasing but also functional surfaces by creating surface geometries that are difficult or impossible to achieve via blasting.  FIG. 1  shows consumer products having surfaces that can be treated using methods described herein, including portable phone  102 , tablet computer  104  and portable computer  106 . Devices  102 ,  104  and  106  have housings or enclosures that not only serve to house internal electronic components, but also provide attractive exterior surfaces that provide aesthetic qualities and affect a user&#39;s experience. For example, a user can choose one brand of device over another brand based on color, shininess, texture and the general look and feel of exterior surfaces of the device. The exterior surfaces can be made of any suitable material, such as metal, plastic, ceramic, silicone or combinations thereof. In some cases, the exterior surfaces are made of an anodizable metal, such as an aluminum alloy. The anodizable metal can be anodized so that a protective oxide coating is provided over the exterior surfaces. 
     One common way of providing an aesthetically appealing textured surface involves a blasting operation.  FIG. 2  shows a section view of substrate  200  undergoing a blasting operation. Blasting generally involves forcibly propelling a blasting media, which includes many particles  202 , against substrate  200  until surface  204  attains a roughness. Particles  202  are generally made of a material that is harder than the material of substrate  200  so that particles  202  create craters  206  on surface  204 . For example, minerals such as silica particles  202  can be used to form craters  206  within metal substrates  200 . The size (e.g., average diameter) of particles  202  and the force with which particles  202  are propelled against substrate  200  determine the size and depth of craters  206 . 
     One of the disadvantages of using a blasting procedure is the irregularity of roughened surface  204  due to the indiscriminant nature of the blasting process. That is, the precise location and force at which each particle  202  impinges against substrate  200  cannot be controlled. One method of providing some regularity is by blasting substrate  200  with a sufficient amount of particles  202  to average out variations in crater  206  size and depth over an entire surface of substrate  200 . However, this only averages out variations on a global scale and does not provide uniformity or control on a localized scale. Additionally, the high pressured blasting media can put very high compressive stresses on substrate  200 . If substrate  200  is relatively thin, this large amount of compressive stress can negatively affect the shape of substrate  200 . For example, the high pressure can deform substrate  200  such that substrate  200  no longer retains a substantially flat overall shape. This factor can be important in applications where it is desirable to have thin substrates. For example, it may be desirable to have relatively thin walls for enclosures of devices  102 ,  104  and/or  106  in order to reduce weight. In some cases, substrate  200  can be under a millimeter thick, which can be deformed using some blasting processes depending on the material of substrate  200 . 
     The methods provided herein can provide a textured surface with features that are uniform and repeatable on a global scale as well as on a localized scale. The methods involve the use of a laser that can produce a laser beam with energy sufficient to affect the surface texture of the substrate. The laser beam energy will depend, in part, on the material of the substrate and a desired texture. In some embodiments, the laser beam ablates a portion of the substrate, thereby precisely removing portions of the substrate. In some embodiments, the laser beam melts a portion of the substrate rather than removing material. The melted material can then resolidify with a shiny surface, effectively polishing the surface of the substrate. Lasers can focus energy to very tight spot sizes, enabling precise sculpting of substrates on a micrometer scale. Thus, unlike blasting techniques, one can control the geometries on individual features on a substrate when using a laser. In addition, the high compressive stresses of a blasting operation can be avoided, thereby reducing deformation of a substrate. 
       FIGS. 3A and 3B  show a plan view and a cross section view, respectively, of part or substrate  300  having features that can be formed using a laser, in accordance with some embodiments. Substrate  300  can be made of any suitable material, including metal, plastic, glass, ceramic or combinations thereof. Surface  308  has multiple features  302  and  304  corresponding to portions of substrate  300  removed by a laser beam, such as by laser ablation. Features  302  are bowl-shaped indentations and features  304  are lines that surround features  302 . Areas  306  correspond to portions of substrate  300  substantially unaffected by the laser beam. In some embodiments substrate  300  is polished prior to the laser treatment so that areas  306  are flat, smooth and shiny. 
     The multiple features  302  and  304  cooperate to form a honeycomb-type pattern on surface  308  to give substrate  300  a particular appearance. Unlike a blasted surface, features  302  and  304  each have a predetermined shape, size and depth and are a predetermined distance apart from one another. This results in design that appears more regular and engineered looking than a blasted surface. In addition, the design is highly repeatable and can be duplicated from substrate to substrate. In some embodiments, the pattern of features  302  and  304  provide a tactile quality to surface  308 , such as a more grippable surface compared to a planar surface. The design can be applied to an entire surface  308  of substrate  300  or just a portion of surface  308  of substrate  300 . 
     Any suitable type of laser can be used to form features  302  and  304 , including CO 2  lasers, solid-state lasers and fiber lasers. The type of laser can depend on the material of substrate  300  and desired shape, size and depth of features  302  and  304 . The overall appearance of surface  308  can vary depending on the size and spacing between features  302  and  304 . Since a laser beam is used, the width and depth of features  302  and  304  can depend on the spot size and energy of the laser beam, as well as a distance between the laser beam source and substrate  300 . These dimensions can be chosen based on design requirements. For example, the size of features  302  and distance between features  302  can be small enough such that features  302  are not individually resolvable by human eye. Features of this small size should be easy to form using many laser systems since the laser beam spot size can be very small. 
     In other embodiments, the size of features  302  and distance between features  302  are large enough be distinguishable individual features as viewed by human eye. In some embodiments, features  302  are each about 1 mm wide and about 0.25 mm deep. In other embodiments, features  302  are each about 100 micrometers wide and 10 micrometers deep. In other embodiments, features  302  are each range between 100 micrometers and 1 mm wide and 10 micrometers and 0.25 mm deep. In some embodiments, the size and distance between features  302  and  304  are designed to be small enough to increase light reflectance or cause interference effects of light waves incident upon surface  308 , which will be described in detail below. In some embodiments, a pulsed laser beam is passed or scanned over surface  308  to form features  302  and  304 . In other embodiments, a continuous laser beam is used, with one or more deflectors positioned to deflect the laser beam away from surface  308  when the laser beam reaches areas  306 . Features  302  and  304  can be formed using a single pass of the laser beam or multiple passes of the laser beam. The number of passes will depend, in part, on the depth of features  302  and  304 . 
       FIGS. 4A-4D  show close up views of substrate  300  undergoing a multiple pass laser operation, in accordance with some embodiments. At  FIG. 4A , surface  308  of substrate  300  is optionally planarized using, for example, one or more polishing and buffing operations. In some embodiments, surface  308  is alternatively or additionally blasted using one or more blasting operations or other texturing operations (e.g., chemical etching), which is not shown.  FIG. 4B  shows substrate  300  after a single pass of a laser beam where a portion of substrate  300  is removed. The laser used to produce the laser beam is tuned to only impinge upon surface  308  where feature  302  is being formed while not impinge upon areas  306 . The depth of feature  302  at this point can vary depending on the energy of the laser beam and the material of substrate  300 . In some embodiments, one laser beam pass forms feature  302  having a depth in the scale of several or tens of micrometers. However, larger depths may be accomplished by tuning laser parameters.  FIG. 4C  shows substrate  300  after a number of passes of the laser beam, where more material from substrate  300  is removed further deepening feature  302 .  FIG. 4D  shows substrate  300  after even more passes of the laser beam where feature  302  is fully formed. 
     Note that each of multiple features  302  can be incrementally formed with each pass of the laser beam. Features  304  can similarly be formed with each pass of the laser beam. In this way, an entire area of features  302  and  304  can be incrementally formed with each laser pass. Since features  304  are shallower than features  302 , features  304  may be fully formed prior to features  302  being completely formed. That is, formation of shallower features  304  can require less passes of the laser beam. In general, the deeper a desired feature, the more laser passes are required. This incremental process can be referred to as laser depth profiling. 
       FIGS. 5A-5C  show substrate  300  before and after optional surface treatment processes to further change the shape of surface  308 . In some cases, some of the surface treatment processes are performed prior to an anodizing process, and are therefore sometimes referred to as pre-anodizing processes.  FIG. 5A  shows substrate  300  with feature  302  formed therein. Insets  503  and  504  show close up views of portions of surface  308  before and after, respectively, an optional surface polishing operation. Suitable surface polishing can include chemical polishing, electropolishing and/or laser polishing. Inset  503  shows microscopic jagged peaks  505  along surface  308  including along feature  302  and areas  306 . Inset  504  shows how a polishing operation can smooth peaks  505  round and smooth out peaks  505 , creating a more uniform surface  308 . After polishing, rounded peaks  505  can specularly reflect more light compared to prior to the polishing, thereby increasing the shininess and glossiness of surface  308 . Chemical polishing generally involves exposing surface  308  to a chemical agent that preferentially removes material at peaks  505 , thereby smoothing out non-uniformities. Electropolishing involves subjecting substrate  300  to an electrolytic operation. For example, substrate  300  can be immersed in an electrolytic bath where substrate  300  serves as an anode. When current is passed through the substrate  300  anode and corresponding cathode, material at peaks  505  become preferentially oxidized and removed. Laser polishing can also smooth out non-uniformities by applying a relatively low amount of energy to surface  308 . The lower laser energy can be sufficient locally melt surface  308  without substantially ablating the material of substrate  300 . Details of some laser polishing operations are described in detail below with reference to  FIGS. 11A-11C and 12A-12C . 
     In some embodiments, substrate  300  is optionally alternatively or additionally subjected to one or more etching operations (not shown). The etching operation can include exposing surface  308  to an acid or alkaline etching solution that selectively removes small amounts of material on a microscopic level, such as along metal grain boundaries if substrate  300  is made of metal. This gives surface  308  a matte appearance. In some embodiments, surface  308  is treated with a combination of polishing and etching operations to give surface  308  a combination of glossy and matte appearance, sometimes referred to as a “satin” look. 
     In some embodiments where substrate  300  includes an anodizable material, such as aluminum, substrate  300  can undergo an anodizing operation.  FIG. 5B  shows substrate  300  after an anodizing process, in accordance with some embodiments. Anodizing involves electrolytically converting a portion of substrate  300  to a corresponding metal oxide layer  506 , with unconverted portion of substrate  300  positioned below metal oxide layer  506 . In this way, metal oxide layer  506  serves as a coating for substrate  300  and surface  308  corresponds as an exterior surface of substrate  300 . The unconverted portion of substrate  300  has feature  510  having a corresponding shape as feature  302  and area  508  having a corresponding shape as area  306 . In some embodiments, the anodizing process can be chosen to provide a particular physical property and/or appearance to substrate  300  as viewed from surface  308 . For example, the anodizing process parameters can be chosen to give metal oxide layer  506  a predetermined thickness, hardness and/or durability. In some embodiments, metal oxide layer  506  is made to have a predetermined amount of light transparency such that most of the visible light incident on metal oxide layer  506  shines through metal oxide layer  506  and reaches underlying substrate  300 . In this way, feature  510  can be visible through metal oxide layer  506 , including gloss, matte or statin appearance provided by any surface treatment operation. Thus, metal oxide layer  506  can be said to have the textured appearance of the substrate  300 . In some embodiments, curvatures of metal oxide layer  506  are designed to act as a sort of lens and focus incoming light to different portions of underlying substrate  300 , such as proximate to features  510 . 
       FIG. 5C  shows substrate  300  after an optional metal oxide layer  506  polishing operation. The polishing operation can include a mechanical polishing and/or buffing operation and can give surface  308  a substantially planar geometry. In some embodiments, metal oxide layer  506  is polished to have a shiny exterior surface. If metal oxide layer  506  is transparent enough, the surface geometry feature  510  and areas  508  can be seen through metal oxide layer  506 , including gloss, matte or satin appearance provided by any surface treatment operation. 
     As described above, laser beam profiling or sculpting can be used to form a vast number of different geometries within a substrate, providing an almost endless amount of designs options. As described above, the geometries can be specifically designed to affect the way light interacts with the substrate and give the substrate a unique appearance.  FIGS. 6A-6C  show cross section views and plan views of substrate  600  that includes faceted feature(s)  602 , in accordance with some embodiments. As shown in  FIG. 6A , faceted feature  602  includes facets  610   a  and  610   b  that are substantially flat surfaces and that are positioned to reflect incoming light. That is, the depth of feature  602  and angles of facets  610   a  and  610   b  relative to surface  606  can be chosen to maximize the reflection of incident light back out of feature  602 . For example, light ray  612  entering feature  602  can reflect off of facet  610   a , then off of facet  610   b , and back out of feature  602 . In this way, light incident upon surface  611  of substrate  600  can be reflected by feature  602 , giving feature  602  a sparkling appearance similar to a faceted diamond. The color of the light reflected will depend on the wavelength of the light source, and in some cases the material of substrate  600 . Facets  610   a  and  610   b  can be formed using laser depth profiling, such as described above with reference to  FIGS. 4A-4D . Substantially each of features  602  can have a predetermined number of facets  610   a  and  610   b  and/or be at a predetermined angle with respect surface  606 , which would not be possible using a blasting process. 
     On a larger scale, substrate  600  can include multiple features  602 , such as shown in the plan view of  FIG. 6B . Each of features  602  has light reflective facets  610   a  and  610   b  that give surface  611  multiple intensified reflection points. The size (e.g., diameter and depth) of features  602  and distance between features  602  can vary depending on design choice. In some embodiments, the diameter of each feature  602  is substantially the same. In other embodiments, the diameters of features  602  vary. In some embodiments, the average diameter of features  602  is small enough such that features  602  are not individually resolvable by human eye. In this case, features  602  will appear as points of sparkle but facets  610   a  and  610   b  will not be resolvable. In other embodiments, the average diameter of features  602  is large enough be distinguishable individual features as viewed by human eye. Features  602  can exist over an entire surface  611  of substrate  600  or only in certain areas of surface  611 . 
     If substrate  600  is made of an anodizable material, substrate  600  can optionally be exposed to an anodizing process, as shown in the cross section view of  FIG. 6C . Note that prior to the anodizing process, substrate  600  can optionally undergo one or more pre-anodizing surface treatment operations (e.g., chemical polishing, electropolishing, laser polishing and/or etching) in order to modify the geometry of surface  611  on a micro-level. For example, a polishing operation can be used to smooth out microscopic non-uniformities and increase the specular reflectance of surface  611 , as described above with respect to  FIG. 5A . The anodizing process converts a portion of substrate  600  to a corresponding metal oxide layer  614 . The portion of substrate  600  that is unconverted remains below metal oxide layer  614  and has feature  618  having a shape corresponding to feature  602  and surface  616  having a shape corresponding to surface  606 . In some embodiments, the shape of metal oxide layer  614  is such that incoming light (e.g., light ray  612 ) is focused toward feature  618 , thereby further intensifying the amount of light reflected off of feature  618 . That is, metal oxide layer  614  can act as a sort of lens. Metal oxide layer  614  can be substantially transparent such that facets  610   a  and  610   b  reflect incoming light in substantially the same manner as described above with reference to  FIG. 6A . At  FIG. 6D , metal oxide layer  614  is optionally planarized such that surface  611  is substantially smooth and flat. 
     In some cases, the features on a substrate are designed to diffract incoming light and produce reflected light having different colors.  FIGS. 7A-7C  show cross section views of substrate  700  having different light diffracting features, in accordance with some embodiments. In general, light diffraction occurs when light encounters an object with a size comparable to its wavelength.  FIG. 7A  shows substrate  700  having features  702  arranged to diffract light. Features  702  can each be formed using a laser process, such as a laser depth profiling process described above. Features  702  have reflective surfaces and are spaced apart from one another by distance  706 . Width  707  and depth  711  of features  702  and/or distance  706  between features  702  are chosen to cause diffraction and interference effects of incident light. That is, features  702  can be a predetermined size and a predetermined distance apart from one another to diffract the incident light. 
     For example, incident light ray  710  impinges on feature  702  at angle θ 1  relative to surface normal  709 . Features  702  reflect and diffracts incident light ray  710  as light ray  712  reflected at angle θ 2  relative to surface normal  709 , and light ray  713  reflected at angle θ 3  relative to surface normal  709 . Light ray  712  and light ray  713  reflecting at different angles can impart different colors or a “rainbow” effect to surface  708 . In some embodiments, this can manifest as visible dots or points of color on surface  708 . The width  707  and distance  706  can be chosen to create a particular light diffraction and interference effects. In some embodiments, width  707  and depth  711  of features  702  and/or distance  706  between features  702  are chosen to create different visual effects based on the angle at which substrate  700  is held. In some cases, the colors of the dots or points of color can change depending on the angle at which substrate  700  is viewed. For example, surface  708  may have a bluish hue when viewed at a first angle and have a reddish hue when viewed at a second angle. 
     Substrate  700  can be made of any suitable material. In some embodiments where substrate  700  is made of an anodizable material, substrate  700  is exposed to an anodizing process, as shown in  FIG. 7B . Note that prior to the anodizing process, substrate  700  can optionally undergo one or more surface treatment operations (e.g., chemical polishing, electropolishing, laser polishing and/or etching). In some embodiments, a polishing operation is performed in order to smooth out microscopic non-uniformities and increase the specular reflectance of surface  708 , as described above with respect to  FIG. 5A . The anodizing process converts a portion of substrate  700  to a corresponding metal oxide layer  714 . The portion of substrate  700  that is unconverted remains below metal oxide layer  714  and has features  718  having shapes corresponding to features  702 . Metal oxide layer  714  can be substantially transparent such that light incident on surface  708  can pass through metal oxide layer  714  and diffract and/or interfere with features  718  of underlying substrate  700 , thereby retaining the light diffraction and interference effects described above. 
     In addition to controlling the clarity of metal oxide layer  714 , thickness  716  of metal oxide layer  714  can be adjusted to add to or create other visual effects. For example, incident light ray  720  is refracted by surface  708  entering metal oxide layer  714 , diffracts off of feature  718  of substrate  700  as light rays  722  and  724 , which are each refracted by surface  708  exiting metal oxide layer  714 . In some cases, the light refraction caused by metal oxide layer  714  can cause interference of reflected light rays  722  and  724 , thereby causing surface  708  to take on different hues. In some embodiments, thickness  716  is chosen to achieve a predetermined amount of refraction and/or interference of light incident surface  708 . At  FIG. 7C , metal oxide layer  714  is optionally planarized such that surface  708  is substantially smooth and flat. The planarizing process can be chosen to reduce the thickness of metal oxide layer  714  to a chosen thickness  726  to create a desired visual effect. In some embodiments, the shape of metal oxide layer  714  is such that incoming light (e.g., light ray  720 ) is focused toward feature  718 , thereby further intensifying the amount of light reflected off of feature  718 . That is, metal oxide layer  714  can act as a sort of lens. 
     The laser forming methods described herein can be used to form features having any suitable geometries and are not limited by the above-described geometries.  FIGS. 8A-8E  show cross section views of substrates having different laser-formed geometries in accordance with some embodiments.  FIG. 8A  shows substrate  800  having surface  804  with features  802  that are in the form of curved protrusions. Substantially flat areas  806  separate features  802  from each other.  FIG. 8B  shows substrate  810  having surface  814  with features  812  in that are curved indentations. Features  812  are positioned close to each other such that sharp peaks  816  are formed on surface  814 .  FIG. 8C  shows substrate  820  with surface  824  with features  822  that are curved protrusions that are positioned close to each other, forming sharp indentations  826 .  FIG. 8D  shows substrate  830  having surface  834  with features  832  in the form of peaks. Features  832  (peaks) and valleys  836  are defined by substantially flat surfaces  838 .  FIG. 8E  shows substrate  840  having surface  844  with features  842  corresponding to sharp peaks with intervening valleys  846 . Flat surfaces  848  and  850  are at different angles relative to surface normal  852 . 
     The features shown in  FIGS. 8A-8E  can be any suitable size (e.g., diameter and depth) and distance apart from each other, depending on design choice and on any desired optical effects. For example, the features may be small enough and/or spaced close enough to cause light diffraction/interference effects. Although the features shown in each of  FIGS. 8A-8E  appear substantially the same size, shape and distance apart, this is not meant to exclude other embodiments where the features are of different size, shape and distance from each other. For example, a substrate can have a combination of sharp peaks/valley as well as curved protrusions and/or indentations. One of skill in the art would recognize that any suitable combination could be used to provide a desired appearance. 
     The laser forming methods described herein can be used to form features that cooperate together to form a particular design on a substrate.  FIGS. 9A-9C  show plan views of substrates having different laser-formed features that form designs, in accordance with some embodiments.  FIG. 9A  shows substrate  900  with parallel lines  902  along surface  904  using a laser process. In some embodiments, scanning a continuous laser beam across surface  904  forms lines  902 . In other embodiments, a pulsed laser beam is used. In some embodiments, each of lines  902  are reflective trenches having a similar cross section as feature  702  or  718  in  FIGS. 7A-7C . Lines  902  can be spaced apart from each other at small enough distances that lines  902  act as a diffraction grating, thereby imparting colors to surface  904  with the colors shifting depending on the viewing angle of surface  904 . In other embodiments, the lines form other geometric shapes, such concentric circles. 
       FIG. 9B  shows substrate  910  with designs  912  and  914  on surface  916  formed using laser processes described herein. Design  912  includes a combination of individual circular shaped features  911  arranged in a symmetric design. As shown, features  911  can have different diameters. In some embodiments, features  911  are indentations within substrate  910  having the same or different depths. In some embodiments, some or all of features  911  have light reflective facets, such as described above with reference to  FIGS. 6A-6D , giving design  912  a sparkling appearance. Design  914  includes laser formed curved lines  913  that combine to form a symbol—in this case eyes, mouth and head of a smiley face. Curved lines  913  can be formed by scanning a continuous or pulsed laser beam along surface  916 . 
       FIG. 9C  shows substrate  920  with lines  922  that combine to form a complex pattern, such as a fractal pattern, on surface  924 . The complex pattern on substrate  920  illustrates how a laser can create complex geometries that cannot be accomplished using blasting or etching. Note that the embodiments illustrated in  FIGS. 9A-9C  are not meant to limit the possibilities within the scope of the present invention. On the contrary,  FIGS. 9A-9C  illustrate how the laser texturing processes described herein can produce light diffracting features, light reflecting features, repeatable shapes, complex shapes, superimposed shapes, and an almost limitless possibility of combination of light interacting features and geometric shapes to provide a desired design on a substrate. 
     The substrates shown in  FIGS. 8A-8E and 9A-9C  can be treated with one or more above-described additional surface treatment operations, such as pre-anodizing processes, in order to provide additional visual effects. For example, chemical polishing, electropolishing and/or laser polishing can be used to smooth out microscopic non-uniformities and increase specular reflectance of the substrate surfaces. Alternatively or additionally, a micro-etching process can add a matte or satin appearance to the substrate surfaces, as described above. 
     The substrates shown in  FIGS. 8A-8E and 9A-9C  can be anodized, if appropriate. Anodizing forms a metal oxide layer that can serve as a protective coating for the substrates. In some embodiments, the anodizing process is tailored based on the geometries of the features and a desired visual affect, such as light refraction effects, that can add to visual effects provided by an underlying substrate. 
     In some embodiments, a substrate has curves, edges or other structures that reflect light different than flat surfaces of the substrate. To illustrate,  FIG. 10  shows a perspective view of substrate  1000 , which includes flat surface  1001 , curved corners  1002  and curved edges  1004 . Substrate  1000  can correspond to a housing for an electronic device. As viewed by an observer, curved corners  1002  and curved edges  1004  will appear glossier than flat surface  1001 , sometimes referred to as specular highlights  1006 . This is due to how curved corners  1002  and curved edges  1004  capture and reflect incident light compared to flat surface  1001 . 
     In some embodiments, the surfaces of substrate  1000  are altered to increase or decrease this specular highlight phenomenon. For example, curved corners  1002  and curved edges  1004  can be treated to intensify the visible difference between curved corners  1002 /edges  1004  compared to flat surface  1001 . One way of accomplishing this is by forming multiple faceted features that each intensify the amount of reflected light at curved corners  1002  and curved edges  1004 , such as described above with reference to  FIGS. 6A-6D . If flat surface  1001  does not have faceted features, curved corners  1002  and curved edges  1004  can appear even brighter than provided by specular highlighting alone. In other embodiments, flat surface  1001  can have multiple faceted features that each intensify reflected light, while curved corners  1002  and curved edges  1004  do not have faceted features. This can give substrate  1000  unique look since the brightness of flat surface  1001  can appear the same as or greater than the brightness of curved corners  1002  and curved edges  1004  due to specular highlighting. Laser texturing on curved surfaces such as curved corners  1002  and curved edges  1004 , can be accomplished by mounting substrate  1000  or the laser on a 5-axis system so that their relative positions can be adjusted and the direction of the laser beam can be controlled in three dimensions. 
     In some embodiments, the surfaces of substrate  1000  are altered to provide diffraction-related colors to substrate  1000 . For example, curved corners  1002  and/or curved edges  1004  can be laser treated to have multiple light diffracting features, such as described above with reference to  FIGS. 7A-7C , or a diffraction grating, such as described above with respect to  FIG. 9A . Alternatively or additionally, flat surface  1001  can be laser treated to have multiple light diffracting features or a diffraction grating. In some embodiments, one or more of flat surface  1001 , curved corners  1002  and curved edges  1004  have a combination of light diffracting features/diffraction grating and light reflective faceted features. In some embodiments, texture differences between flat surface  1001  and curved corners  1002 /edges  1004  are gradual such that there is no visibly distinct transition between varying textured surfaces. 
     Flat surface  1001  and curved corners  1002 /edges  1004  of substrate  1000  can be treated with one or more above-described surface treatment operations in order to provide additional visual effects. In some cases, the type of surface treatment will vary depending upon the type of laser texture and a desired final surface texture. For example, surface  1001  or curved corners  1002 /edges  1004  can be polished using chemical, electrochemical and/or laser polishing to increase its specular reflectance or chemically etched to decrease its specular reflectance. If substrate  1000  is anodizable, it can be anodized to provide a protective metal oxide layer on substrate  1000 . In some cases, the metal oxide layer is designed to add visual effects, such as light refraction effects described above with respect to  FIGS. 7A-7C . 
     Note that corners  1002  and edges  1004  can be charge concentrators during the anodizing process. Therefore, the metal oxide layer over corners  1002  and edges  1004  tends to grow faster and end up being thicker. Thus, in some embodiments, more or different types of laser features are formed at flat surface  1001  compared to corners  1002  and edges  1004  to increase the rate of anodizing at flat surface  1001 . This can create a metal oxide layer having a more uniform thickness across flat surface  1001 , corners  1002  and edges  1004 . 
     As previously described, laser polishing can be used to smooth a surface of a substrate, in addition to or instead of other polishing operations such as chemical polishing and electropolishing.  FIGS. 11A-11C  show cross section views and a plan view of substrate  1100  undergoing a laser polishing process in accordance with some embodiments.  FIG. 11A  shows a close up cross section view of substrate  1100  prior to the laser polishing operation. Surface  1102  of substrate  1100  is uneven, such a blasted surface formed by impingement of blasting media. Surface  1102  has multiple peaks  1104  that can give surface  1102  a dull or matte appearance. It should be noted that the laser polishing process described herein are not limited to blasted surfaces and that a surface having any suitable geometry for polishing can be used. 
       FIG. 11B  shows a cross section view of substrate  1100  after portion  1106  of surface  1102  is treated using a laser polishing operation. Laser polishing involves directing a laser beam having a relatively low energy at surface  1102 , specifically at portion  1106 . Remainder portion  1108  of surface  1102  is substantially unaffected by the laser polishing operation, therefore retains a blasted surface texture with peaks  1104 . The relatively low energy laser beam locally melts the material of substrate  1100  at portion  1106  without substantially ablating it, which causes peaks  1104  to round out (illustrated as rounded peaks  1104   a ) or to disappear altogether. The material at portion  1106  then re-solidifies with the rounded peaks  1104   a  or substantially no peaks. As a result, portion  1106  will specularly reflect light incident on surface  1102  more than remainder portion  1108 . That is, portion  1106  will be shinier and glossier than remainder portion  1108 . In some embodiments, portion  1106  is laser polished to a mirror shine. In addition, portion  1106  can be tactilely smoother than remainder portion  1108 . 
       FIG. 11C  shows a plan view of substrate  1100  after the laser polishing operation. As shown, laser polished portion  1106  can be in the form of a symbol or icon that is visually distinguishable from remainder portion  1108  that is left unpolished. It should be noted that portion  1106  could have any suitable shape and size based on the capabilities of the laser used for the polishing operation. For example, portion  1106  can be in the shape of text or as a regular pattern of dots or lines adjacent to remainder portion  1108 . 
     Any suitable type of laser can be used for laser polishing, including a CO 2  laser, solid-state laser or fiber laser. The laser beam can be a pulsed laser beam or a continuous laser beam. The lower energy laser beam sufficient for laser polishing without ablation can be accomplished by adjusting the laser power, the laser beam duration/pulse, or a combination thereof. The type of adjustment will depend, in part, on the type of laser and the material of substrate  1100 . These adjustments can also be used to control an amount of melting of substrate  1100 . In this way, laser polishing can accomplish unique polishing effects that may not be attainable using traditional chemical and/or electrochemical polishing operations. 
       FIGS. 12A-12C  show close up cross section views and a plan view of substrate  1200  undergoing an alternative laser polishing operation.  FIG. 12A  shows substrate  1200  prior to the laser polishing operation having multiple peaks  1204  that can give surface  1202  a dull or matte appearance. Surface  1202  can correspond to a blasted surface.  FIG. 12B  shows substrate after a laser polishing process where peaks  1204  are rounded off to a lesser degree than the embodiments shown in  FIGS. 11A-11C . This can be accomplished by using an even lower laser energy than described above with reference to  FIGS. 11A-11C . The lower laser energy rounds peaks  1204  increasing the specular reflectivity of surface  1202 , while still leaving the general shape of peaks  1204  intact. In some embodiments, surface  1202  is further treated with an etching operation that gives surface  1202  a combination of glossy and matte appearance, or “satin” appearance.  FIG. 12C  shows a plan view of substrate  1200  with portion  1208  having the satin appearance and portion  1206  having a mirror shine. Portion  1206  can be polished using one or more mechanical, chemical, electrochemical and laser polishing processes and correspond to a design such as a logo. 
     In some cases, a laser polishing operation is used in place of a chemical or electrochemical polishing operation. This can be due to the high degree of polished control that laser polishing can provide compared to chemical and electrochemical polishing, as described above. In addition, laser polishing can simplify a manufacturing process flow and decrease production time. This is because traditional chemical polishing or electrochemical polishing operations generally require masking of areas that are not polished in order to avoid exposure of these areas to the chemical/electrochemical solutions. For example, forming the varied textured surface  1202  of substrate  1200  using traditional methods may require the following steps: First, surface  1202  is mechanically polished so that portion  1206  and portion  1208  attain a mirror shine. Next, portion  1206  is masked. Subsequently, portion  1208  is blasted and exposed to a chemical or electrochemical polishing operation to attain a satin appearance. Then, the mask is removed from portion  1206 . The masking is necessary in order to prevent exposure of portion  1206  to the harsh conditions of chemical or electrochemical polishing, which would destroy its mirror shine. Then, substrate  1200  undergoes an anodizing process to from a protective metal oxide layer over surface  1202 . 
     In contrast, a laser polishing process can be used to locally produce a desired surface quality without masking. The following two examples are ways of creating a varied textured surface, such as surface  1202 , using laser polishing processes described herein. 
     Example 1 
     Surface  1202  is polished to a mirror shine using one or more of mechanical, chemical, electrochemical and laser polishing. Next, indented features are formed on portion  1208  using a textured laser process. The indented features can be tailored to appear like a blasted surface, such as a pseudo-random pattern. In other embodiments, the indented features form a regular pattern or a predetermined design described above. Portion  1208  can also be laser polished to round peaks within the laser textured surface and add specular reflectance to portion  1208 . Since laser texturing allows for fine control, portion  1206  is not affected by the laser texturing process and retains its mirror shine without use of a mask. Next, surface  1202  can be anodized. 
     Example 2 
     Substrate  1200  is formed using a machining process. Next, indented features are formed on portion  1208  using a textured laser process and laser polished to add specular reflectance. In addition, the laser only applies a laser polishing process to portion  1206  that locally melts material of substrate  1200  and forms a mirror polish on portion  1206 . Portion  1206  and portion  1208  can be laser processed using a single laser operation or separate laser operations. 
     Both of the examples described above can be used to form the varied textured surface  1202  without the use of a mask. In some cases, the varied texture surface can be formed entirely using laser process without the use of mechanical, chemical and electrochemical polishing. In this way, laser texturing and polishing can greatly simplify the manufacturing of substrate  1200 . Likewise, the laser texturing and polishing process described herein can be used in any suitable combination to form other predetermined patterns and designs and create other visual effects on a substrate. 
       FIG. 13  shows flowchart  1300  indicating a laser texturing and anodizing process in accordance with some embodiments. At  1302 , a surface of a substrate is optionally treated prior to a laser texturing operation. The surface treatment can include one or more of mechanical, chemical, electrochemical and laser polishing, as well as other texturing processes such as blasting and/or chemical etching. The substrate can be made of any suitable material, including metal (e.g., aluminum alloy or stainless steel), glass, ceramic, plastic, or a combination thereof. 
     At  1304 , the surface of the substrate is laser textured by impinging a laser beam at the surface having a laser beam energy sufficient to ablate portions of the substrate. The laser beam can be finely controlled to form intricate patterns and designs on the substrate, or can be used to form a pseudo-random pattern that mimics a blasted surface. In some embodiments, the laser beam forms features with geometries specifically designed to provide light reflecting and/or diffracting effects that give the substrate surface a unique appearance. 
     At  1306 , the laser textured surface is optionally modified using one or more additional surface treatments. In cases where the substrate is to be anodized, the surface treatments can be referred to as pre-anodizing processes. In some cases, the surface treatments include conventional processes, such as chemical polishing and/or chemical etching. In some embodiments, the surface treatments include one or more additional laser processes, such as a laser polishing operation. In one embodiment, the surface treatment includes chemical polishing to round off laser formed peaks and add specular reflection, then acid and/or alkaline etching to add micro-texture and creating a satin appearance. In some embodiments, the type of surface treatment process depends on the geometry of the textured surface and on a desired final appearance of the substrate. 
     At  1308 , for substrates that are anodizable, the substrate is optionally anodized in order to form a protective metal oxide coating. In some embodiments, the anodizing process is customized based on the geometry of the textured surface and on a desired visual effect of the substrate. For example, the anodizing process can be tuned to create a substantially transparent metal oxide layer such that the laser formed features within the substrate are clearly viewable. In some embodiments, the anodizing process is tuned to create a metal oxide layer having a predetermined thickness that adds visual effects to the surface of the part via refraction of incoming light. In some embodiments, different surface portions of the substrate are treated with different anodizing processes based on laser formed features in the different surface portions. In some embodiments, the metal oxide layer is polished to have a shiny exterior surface. 
     The foregoing description, for purposes of explanation, used 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 specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described 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: 20150825
Publication Date: 20200317
Grant Date: 20200317
Priority Date: 20150313
Inventors: MALONEY, Max A.
NASHNER, MICHAEL S.
NOVAK, SEAN R.
Assignee: APPLE INC
CPC Classifications: [{"code": "B44C1/228", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/354", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/16", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K26/3576", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K2103/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25F3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/355", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/16", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K26/355", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/3576", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K2103/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25F3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/354", "inventive": true, "first": false, "tree": "[]"}, {"code": "B44C1/228", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 56887501