PATENT DOCUMENT

Publication Number: US-10184190-B2
Application Number: US-201514622443-A
Country: US
Kind Code: B2

Title: White appearing anodized films

Abstract:
The embodiments described herein relate to forming anodized films that have a white appearance. In some embodiments, an anodized film having pores with light diffusing pore walls created by varying the current density during an anodizing process is described. In some embodiments, an anodized film having light diffusing micro-cracks created by a laser cracking procedure is described. In some embodiments, a sputtered layer of light diffusing aluminum is provided below an anodized film. In some embodiments, light diffusing particles are infused within openings of an anodized layer.

Claims:
What is claimed is: 
     
       1. A metal part having a coating disposed over a reflective surface of the metal part, the coating comprising:
 a metal oxide layer that allows light incident thereon to pass therethrough and reflect off the reflective surface, the metal oxide layer including:
 an ordered region having parallel pore structures that are arranged in an ordered manner and that extend from a top surface of the metal oxide layer to the reflective surface such that, of an amount of light incident onto the top surface of the metal oxide layer, a portion of the amount of light passes through the parallel pore structures and is reflected by the reflective surface, and 
 light diffusing melted portions that include micro-cracks, wherein the micro-cracks are configured to diffusely reflect light incident thereon, and a distance between centers of the light diffusing melted portions is equal to diameters of the light diffusing melted portions such that at least a remaining portion of the amount of light incident onto the top surface is diffusely reflected by the micro-cracks and combines with the amount of light reflected off the reflective surface to impart a white appearance to the metal oxide layer. 
 
 
     
     
       2. The metal part of  claim 1 , wherein the remaining portion of the amount of light that is diffusely reflected by the micro-cracks is based on an average size of the light diffusing melted portions. 
     
     
       3. The metal part of  claim 1 , wherein the portion of the amount of light reflected by the reflective surface corresponds to an average separation distance between the parallel pore structures. 
     
     
       4. The metal part of  claim 1 , wherein diameters of the light diffusing melted portions are between 80 and 200 micrometers. 
     
     
       5. The metal part of  claim 1 , wherein the light diffusing melted portions have irregular porous structures. 
     
     
       6. A metal part having a metal oxide layer disposed over a reflective surface of the metal part, the metal oxide layer comprising:
 light diffusing melted portions that extend from a top surface of the metal oxide layer and towards the metal part, wherein (i) a distance between centers of the light diffusing melted portions is equal to diameters of the light diffusing melted portions, and (ii) the light diffusing melted portions include micro-cracks that are formed therein such as to cause a first amount of light incident onto the micro-cracks to be diffusely reflected thereon; and 
 a translucent intervening portion that separates the light diffusing melted portions, the translucent intervening portion having highly ordered porous structures that extend from the top surface of the metal oxide layer to the reflective surface, wherein the translucent intervening portion is configured to allow a second amount of light incident thereon to pass therethrough and specularly reflect off the reflective surface, and the first amount of light that is diffusely reflected by the micro-cracks combines with the second amount of light specularly reflected off the reflective surface to impart a white appearance to the metal oxide layer. 
 
     
     
       7. The metal part of  claim 6 , wherein the light diffusing melted portions are characterized as having a crystalline microstructure, and the translucent intervening portion is characterized as having an amorphous microstructure. 
     
     
       8. The metal part of  claim 6 , wherein the highly ordered porous structures are parallel to each other. 
     
     
       9. The metal part of  claim 6 , wherein the metal oxide layer has an L value ranging between 85 to 100. 
     
     
       10. The metal part of  claim 6 , wherein the micro-cracks have lengths between about 0.5 and 30 microns. 
     
     
       11. An enclosure for an electronic device, the enclosure having a metal oxide layer disposed over a metal substrate having a reflective surface, the metal oxide layer comprising:
 light diffusing melted portions having micro-cracks arranged at different angles relative to a top surface of the metal oxide layer, wherein a distance between centers of the light diffusing melted portions is equal to diameters of the light diffusing melted portions, such that the micro-cracks are configured to allow a first portion of light incident onto the micro-cracks to be diffusely reflected thereon; and 
 translucent intervening portions that separate the light diffusing melted portions, wherein the translucent intervening portions include parallel pore structures that are configured to allow a second portion of light incident onto the top surface of the metal oxide layer to pass therethrough and specularly reflect off the reflective surface, wherein the first portion of light diffusely reflected off the micro-cracks combines with the second portion of light specularly reflected off the reflective surface to impart a white appearance to the metal oxide layer. 
 
     
     
       12. The enclosure of  claim 11 , wherein the first portion of light corresponds to an average size of light receiving surfaces of the light diffusing melted portions. 
     
     
       13. The enclosure of  claim 11 , wherein the light diffusing melted portions are characterized as having a microstructure that is different than the translucent intervening portions. 
     
     
       14. The enclosure of  claim 11 , wherein the light diffusing melted portions are characterized as having diameters between 80 and 200 micrometers. 
     
     
       15. The enclosure of  claim 11 , wherein the light diffusing melted portions include crystalline metal oxide.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of U.S. patent application Ser. No. 14/240,252 filed Feb. 21, 2014 entitled “Method of Forming White Appearing Anodized Films By Laser Beam Treatment”, which is a 35 U.S.C. § 371 national phase entry of PCT/US2013/047163 filed Jun. 21, 2013 entitled “White Appearing Anodized Films And Methods For Forming The Same”, which claims priority to U.S. Provisional Application Ser. No. 61/663,515 filed Jun. 22, 2012, entitled “Anodization”, U.S. Provisional Application Ser. No. 61/701,568 filed Sep. 14, 2012 entitled “Anodization”, and U.S. Provisional Application Ser. No. 61/702,202 filed Sep. 17, 2012 entitled “Anodization”, each of which are incorporated herein by reference in its entirety. 
    
    
     FIELD 
     This disclosure relates generally to anodizing processes. More specifically, methods for producing an anodized film having a white appearance are disclosed. 
     BACKGROUND 
     Anodizing is an electrolytic passivation process used to increase the thickness of a natural oxide layer on a surface of metal parts where the part to be treated forms the anode electrode of an electrical circuit. Anodizing increases corrosion resistance and wear resistance, can provide better adhesion for paint primers and glues. The anodized film can also be used for a number of cosmetic effects. For example, techniques for colorizing anodized films have been developed that can provide an anodized film with a perceived color based, in part, upon a type and amount of light reflection at the anodized film surface. A particular color can be perceived when a light of a specific frequency is reflected off the surface of the anodized film. 
     In some cases, it can be desirable to form an anodized film having a white color. However, conventional attempts to provide a white appearing anodized film have resulted in anodized films that appear to be off-white, muted grey and milky white, and not a crisp and clean appearing white that many people find appealing. 
     SUMMARY 
     This paper describes various embodiments that relate to metal oxide films and methods for forming the same. Embodiments presented herein describe white appearing metal oxide films and methods for forming the same. 
     According to one embodiment, a method is described. The method involves sequentially varying a current density while forming a layer of aluminum oxide on an aluminum substrate. The layer of aluminum oxide is substantially opaque and reflects substantially all wavelengths of white light incident thereon. 
     According to another embodiment, a metal substrate is described. The metal substrate has a protective film disposed over an underlying metal surface. The protective film has a porous structure with a white appearance, the porous structure having a number of pores. At least a portion of the pores includes irregular pore walls having a number of sequentially repeating wide portions and narrow portions. The sequentially repeating wide portions and narrow portions provide a number of visible light reflecting surfaces positioned at various orientations with respect to a top surface of the protective film such that substantially all visible wavelengths of light incident the top surface diffusely reflect from the visible light reflecting surfaces and exit the top surface. 
     According to an additional embodiment, a method for forming micro-cracks within a porous structure of an anodized film such that the anodized film appears white is described. The method includes forming a pattern of melted portions within the porous structure by scanning a pulsed laser beam over a top surface of the anodized film. The method also includes forming a pattern of crystallized metal oxide portions within the anodized film by allowing the pattern of melted portions to cool and transform into crystalline form. During the cooling, a number of micro-cracks form within the pattern of crystallized metal oxide portions. The micro-cracks diffusely reflect nearly all visible wavelengths of light incident the crystallized metal oxide portions. 
     According to a further embodiment, a metal part having an anodized film with a white appearance disposed over an underlying surface of the metal part is described. The anodized film includes a porous metal oxide structure. The anodized film also includes a pattern of crystallized metal oxide portions within the porous metal oxide structure, the pattern of crystallized metal oxide portions having a number of micro-cracks. The micro-cracks have a plurality of visible light reflecting surfaces arranged in varied orientation with respect to an exposed surface of the anodized film. The visible light reflecting surfaces diffusely reflect visible light incident the crystallized metal oxide portions, contributing an opaque and white appearance to the metal part. 
     According to another embodiment, a method for forming an anodized film on a substrate is described. The method includes sputtering a layer of aluminum onto a substrate, the sputtered aluminum layer having a surface with a first roughness. The method also includes converting a first portion of the sputtered aluminum layer to an anodized film. An underlying second portion of the sputtered aluminum layer has a second surface that has a second roughness associated with the first roughness. The second surface is sufficiently rough such that white light incident to an exposed surface of the anodized layer travels through the anodized layer, diffusely reflects off the second surface, and exits the anodized layer. 
     According to an additional embodiment, a method for producing an anodized film that appears white is described. The method involves creating a number of openings within the anodized film. The openings having an average size and shape suitable for accommodating a number of light reflective particles. The light reflective particles have a white appearance due to the presence of multiple visible light diffusing surfaces on the light reflective particles. The method also involves infusing the light reflective particles within at least a portion of the openings. The white appearance of the light reflective particles imparts a white appearance to the anodized film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments. 
         FIGS. 1A-1D  illustrate various reflection mechanisms for providing a perceived color or quality of an object. 
         FIG. 2  illustrates a cross section view of a part with an anodized film formed using standard anodizing conditions. 
         FIG. 3  illustrates a cross section view of a part with a white anodized film formed using varied current densities. 
         FIGS. 4A and 4B  show graphs indicating current density as a function of time during two different varied current density anodizing processes. 
         FIG. 5  shows a graph indicating current density as a function of time during another varied current density anodizing process. 
         FIG. 6  shows a flowchart indicating steps for forming a white anodized film having irregular or textured pore walls using a varied current density anodizing process. 
         FIGS. 7A-7C  illustrate top and cross section views of a part having a white anodized film after undergoing a laser cracking procedure. 
         FIG. 8  shows a flowchart indicating steps for forming a white anodized film having micro-cracks using a raster scanning pulsed laser beam. 
         FIGS. 9A-9C  illustrate different laser scan samples with varying spot density, laser power and spot size settings. 
         FIG. 9D  illustrates a graph showing specular reflected light intensity as a function of viewing angle for different anodized film samples. 
         FIG. 10  shows a flowchart indicating steps for tuning a laser cracking process for producing a white anodized film having a target amount of diffuse and specular reflectance. 
         FIG. 11  illustrates a cross section view of a part with a white anodized film formed using a combination of varied current density anodizing and laser cracking procedures. 
         FIG. 12  shows a flowchart indicating steps for forming a white anodized film formed using a combination of varied current density anodizing and laser cracking procedures. 
         FIGS. 13A-13B  illustrate cross section views of a part undergoing a reflective layer depositing process following by an anodizing process. 
         FIG. 14  shows a flow chart indicating steps for forming a white anodized film by depositing an underlying reflective layer. 
         FIGS. 15A-15C  illustrate cross section views of a part undergoing a pore infusion process. 
         FIGS. 16A and 16B  illustrate cross section views of a part undergoing a micro-crack infusion process. 
         FIGS. 17A-17D  illustrate top-down and cross section views of a part undergoing laser drilling, anodizing and light reflective particle infusion processes. 
         FIG. 18  illustrates a light reflecting particle pore infusion process using an electrophoresis technique. 
         FIG. 19  shows a flow chart indicating steps for forming a white anodized film by infusing light reflective particles within openings of the anodized film. 
     
    
    
     DETAILED DESCRIPTION 
     Representative applications of methods according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     This application relates to various embodiments of methods and apparatus for anodizing an aluminum surface in such a way that the resulting anodized film appears white. The white appearing anodized films are well suited for providing both protective and attractive surfaces to visible portions of consumer products. For example, methods described herein can be used for providing protective and cosmetically appealing exterior portions of metal enclosures and casings for electronic devices, such as those manufactured by Apple Inc., based in Cupertino, Calif. 
     In general, white is the color of objects that diffusely reflect nearly all visible wavelengths of light. Thus, an anodized film can be perceived as white when nearly all visible wavelengths of light incident a top surface of the anodized film are diffusely reflected.  FIG. 1A , shows how incident light can be diffusely reflected off a surface and scattered in many directions. Diffuse reflection can be caused by incident light reflecting off of multi-faceted surfaces at a top surface or within an object. For example, facets of ice crystals that form a snowflake diffusely reflect incident light, rendering the snowflake white in appearance. This is in contrast to specular reflection ( FIG. 1B ) where light is reflected in one direction, colored matte appearing objects ( FIG. 1C ) where some wavelengths of light are absorbed and only certain wavelengths of light are diffusely reflected, and black objects ( FIG. 1D ) where substantially all the wavelengths of light are absorbed and no light is reflected. 
     In the described embodiments, techniques involve forming white appearing anodized films. In some embodiments, the anodized film appears white due to a combination of specular and diffuse reflection of all wavelengths present in white light due to structural features within the anodized film. In some embodiments, the anodized film appears white due to the presence of embedded particles that essentially “dye” the anodized film white. In some embodiments, the anodized film appears white due to the presence of an underlying light diffusing and reflecting layer. In some cases, two or more described techniques for producing white appearing anodized films can be combined. 
     The amount of perceived whiteness of an anodized film can be measured using any of a number of color analysis techniques. For example a color opponent color space, such as L,a,b (Lab) color space (L indicates the amount of lightness, and a and b indicate color-opponent dimensions) can be used to as a standard from which an objective determination of the perceived whiteness of different anodized film samples can be made. In some embodiments described herein, optimum white anodized films have an L value ranging from about 85 to 100 and a,b values of nearly 0. Therefore, these anodized films are bright and color-neutral. 
     As used herein, the terms anodized film, anodized layer, anodization film, anodization layer, oxide layer, and oxide film may be used interchangeably and can refer to any appropriate metal oxide film. The anodized films are formed on metal surfaces of a metal substrate. The metal substrate can include any of a number of suitable metals. In some embodiments, the metal substrate includes pure aluminum or aluminum alloy. In some embodiments, suitable aluminum alloys include 1000, 2000, 5000, 6000, and 7000 series aluminum alloys. 
     Modifying Pore Walls 
     One method for forming a white appearing anodized film involves forming irregular pore walls during the anodizing process.  FIG. 2  illustrates a cross section view of part  200  with anodized film  202  formed using standard anodizing conditions. During a standard anodizing process, a top portion of metal substrate  204  is converted to a layer of metal oxide, or anodized film  202 , forming multiple self-organizing pores  206  within anodized film  202 . Pores  206  are elongated nanometer scale voids that are open at top surface  210  and that are defined by pore walls  208 . As shown, pores  206  are highly ordered in that they are each arranged in perpendicular orientation with respect to top surface  210 , and are equidistant and in parallel orientation with respect to each other. 
     Anodized film  202  is generally translucent in appearance since much of the incident white light coming in from top surface  210  can transmit through anodized film  202  and reflect off of at top surface of underlying substrate  204 . For example, light ray  212  can enter from top surface  210 , pass through anodized film  202 , reflect off of a surface of underlying substrate  204 , pass again through anodized film  202 , and exit at top surface  210 . Since pore walls  208  are generally smooth and uniform, they do not substantially interfere with the transmission of light ray  212  through anodized film  202 . Thus, as viewed by an observer from top surface  210 , anodized film  202  appears translucent and a viewer would see underlying substrate  204 . Since substrate  204  would reflect light of a particular wavelength or range of wavelengths, part  200  would appear to have a color close to the color of underlying substrate  204 . If underlying substrate  204  is smooth and reflective, the incident light can specularly reflect off underlying substrate  204  (as in a mirror in which an angle of incidence is equal to an angle of reflection). For example, light ray  214  can specularly reflect off underlying substrate  204  in the same direction as light ray  212 , giving part  200  a shiny reflective look. It should be noted that anodized film  202  is generally translucent, and not completely transparent, since smaller amounts of incident light will not completely pass through anodized film  202  to underlying substrate  204 . 
     Methods described herein can be used to form an anodized film that has an opaque and white appearance as viewed from a top surface.  FIG. 3  illustrates a cross section view of part  300  with anodized film  302  formed using anodizing techniques in accordance with described embodiments. During the anodizing process, a top portion of metal substrate  304  is converted to a layer of metal oxide, or anodized film  302 . As shown, pores  306  have pore walls  308  that are irregular in shape. Irregular pore walls  308  have multiple tiny surfaces that can act as reflection points for incident light. For example, light ray  312  can enter from top surface  310 , pass through a portion of anodized film  302 , reflect off of a first surface of irregular pore walls  308 , pass through another portion of anodized film  302 , and exit at top surface  310 . Similarly, light ray  314  can enter from top surface  310 , pass through a portion of anodized film  302 , reflect off of a second surface of irregular pore walls  308 , pass through another portion of anodized film  302 , and exit at top surface  310 . Since light rays  312  and  314  do not reach substrate  304 , anodized film  302  is not transparent, i.e., opaque. That is, a viewer observing from top surface  310  would not be able to see underlying substrate  304 . 
     In addition to being opaque, anodized film  302  also has a white appearance. As described above, objects appear white when they diffusely reflect, or scatter, nearly all visible wavelengths of light. The multiple surfaces of irregular pore walls  308  arranged in varied angles can scatter incident visible light at multiple different angles. For example, light ray  312  reflecting off the first surface of pore walls  308  exits at top surface  310  at a first angle, while light ray  314  coming in at the same angle as light ray  312  reflects off the second surface of pore walls  308  exits at top surface  310  at a second angle different from the first angle. Since irregular pore walls  308  have many surfaces arranged in many different angles relative to top surface  310  and each other, different light rays entering anodized film  302  at the same angle will exit anodized film  302  at many different angles. In this way, incident visible light can be diffusely reflected and impart a white appearance to anodized film  302 . 
     Techniques for forming a white anodized film with irregular pore walls, such as anodized film  302 , include performing an anodizing process while applying a pulsed current density. In general, the current density can affect the width of the pores, with higher current densities generally forming wider pores and lower current densities generally forming narrower pores. By varying the current density during pore growth, the pores are wide in some portions and narrow in other portions. For example, pores  306  can have wide portions having a first diameter  316  formed during high current density conditions and narrow portions having a second diameter  318  formed during low current density conditions, thereby forming irregular pore walls  308 . 
       FIG. 4A  shows graph  400  indicating current density (e.g., A/dm 2 ) as a function of time (e g, minutes) during an anodizing process with varied current density, in accordance with some embodiments. During the anodizing process, a substrate is placed in an anodizing solution and acts as anode when a voltage is applied. As the anodization process converts part of the substrate to a metal oxide, the voltage is increased to a high current density B and decreased to a low current density A at different intervals. As shown, during time interval a, the current density is ramped up from 0 to high current density B. The current density is maintained at high current density B for time interval b. During time interval b, the widths of the pores forming within the anodized film are relatively wide. During time interval c, the current density is decreased to low current density A. The current density is maintained at low current density A for time interval d. During time interval d, the pores continue to form but have narrower widths relative to pore formation during time interval b. In some embodiments, time intervals a, b, c and d are on the order of minutes. The current density is then pulsed, i.e., increased to high current density B and decreased to low current density A, for a series of times until the anodized film reaches a target thickness and the anodizing process is complete. In this way, the widths of the pores can vary as they are being formed, creating irregular pore walls, such as pore walls  308  of  FIG. 3 . 
       FIG. 4B  shows graph  420  similar to graph  400  of  FIG. 4A , but with non-linear increases and decreases in the current density. For example, during time interval a, the current density is ramped up from 0 to high current density B in a non-linear fashion. Likewise, during time interval c, the current density is decreased to low current density A in a non-linear fashion. The manner in which the current density is increased and decreased can affect the shape of the pore walls in the resultant anodized film. 
     The relative time periods of intervals a, b, c, and d presented in graphs  400  and  420  are merely illustrative of particular embodiments and do not necessarily dictate the relative time periods of other embodiments. For instance, time intervals b can be shorter relative to a, c, and d, thereby applying very short pulses of high current density. In other embodiments, one or more time intervals a, b, c, and d are the same.  FIG. 5  shows graph  500  indicating current density (e.g., A/dm 2 ) as a function of time (e.g., minutes) during an anodizing process with evenly spaced short pulses of high current density, in accordance with additional embodiments. As shown, during time interval a, the current density is ramped up from 0 to high current density B. The current density is maintained at high current density B for time interval b. During time interval b, the widths of the pores forming within the anodized film are relatively wide. During another time interval b, the current density is decreased to low current density A. The current density is maintained at low current density A for an additional time interval b, during which time the pores continue to form but have narrower widths relative to pore formation during high current density B. In some embodiments, time interval b is on the order of minutes. In other embodiments, time interval b is on the order of seconds. The current density is then pulsed, i.e., increased to high current density B and decreased to low current density A, for a series of times until the anodized film reaches a target thickness and the anodizing process is complete. In some embodiments, the anodizing process can involve applying a series of very short pulses of high current density followed by a series of longer pulsed of high current density. These different parameters can affect the shape and irregularity of the pore walls in different ways, producing slight variations of whiteness of the resulting anodized film. 
     The low and high current density values described above with reference to  FIGS. 4A, 4B , and  5  can vary depending upon the desired pore wall shape and on particular application requirements. In some embodiments, high current density B ranges between about 2.0 and 4.0 A/dm 2  and low current density A ranges between about 0.5 and 2.0 A/dm 2 . Since the applied current density is related to voltage, the process can also be varied with respect to high and low voltage values. The target thickness of the anodized film can also vary depending, in part, on particular application requirements. In some embodiments, the anodizing process is performed until a target thickness of about 20 to 35 microns is achieved. 
     In addition to controlling the shape and irregularity of the pore walls, the pores density can be controlled during the anodizing process by adjusting the anodizing bath temperature. In general, the higher the bath temperature, the thinner the metal oxide material is formed between the pores and the higher the pore density. The lower the bath temperature, the thicker the metal oxide material is formed between the pores and the lower the pore density. Higher pore density is directly associated with the amount of pore walls that can act as reflective surface for incident light. Therefore, the higher the pore density, the higher the amount of irregularly shaped pore walls and the more light scattering medium provided for diffusing incident light. As such, higher bath temperatures generally produce whiter anodized film than lower bath temperatures. However, other factors, such as durability of the anodized film, should also be considered when choosing the bath temperature. In some embodiments, an anodizing bath temperature of about 0° C. to about 25° C. is used. 
       FIG. 6  shows flowchart  600  indicating steps for forming a white anodized film having irregular or textured pore walls using a varied current density anodizing process, in accordance with some embodiments. At  602 , the current density during an anodizing process is ramped up to a high current density, such as high current density B of  FIGS. 4 and 5 . At  604 , the current density is maintained at the high current density for a first time interval. During the first time interval, wide portions of the pores are formed. At  606 , the current density is decreased to a low current density, such as low current density A of  FIGS. 4 and 5 . At  608 , the current density is maintained at the low current density for a second time interval. During the second time interval, narrow portions of the pores are formed. Note that in some embodiments, the current density is first ramped to the low current density, followed by increasing to the higher current density. At  610 , it is determined whether the target thickness of the anodized film is achieved. If the target thickness is achieved, the anodizing process is complete. If the target thickness has not yet been achieved, processes  604 ,  606 ,  608 , and  610  are repeated until the target thickness is achieved. In some embodiments, the target thickness is between about 5 and 50 microns. In some embodiments, the target thickness is achieved at between about 20 and 90 minutes. The resultant anodized film has pores with irregular pore walls that can diffusely reflect incident light, thereby imparting a white and opaque appearance to the anodized film. 
     Note that before and after the anodizing process of flowchart  600 , one or more of any suitable pre and post anodizing processes can be implemented. For example, prior to anodizing, the substrate can undergo one or more cleaning, polishing and blasting operations. In addition, after anodizing, the anodized film can be colored using a dye or electrochemical coloring process. In some embodiments, the surface of the anodized film is polished using mechanical methods such as buffing or lapping. 
     Forming Micro-Cracks within an Anodized Film 
     Another method for forming a white anodized film involves forming localized micro-cracks at the surface portions or sub-surface portions of the anodized film. The cracks can be formed by raster scanning a pulsed laser beam over a surface of the anodized film.  FIGS. 7A and 7B  illustrate a top view and a cross section view, respectively, of part  700  after undergoing a laser cracking procedure, in accordance with described embodiments. Part  700  includes anodized film  702  formed over underlying substrate  704 . During the laser cracking procedure, a pulsed laser beam is raster scanned over top surface  710  of anodized film  702 . The raster scanning produces a pattern of spot areas  714 , which represent areas of anodized film  702  that have been exposed to a pulse of a laser beam during the raster scanning. As shown, spot areas  714  are arranged in a pattern surrounded by unexposed areas  720 . The size of each spot area  714  can be measured in terms of spot diameter  716  and can be controlled by laser settings. Spacing  718  between spot areas  714  can be controlled by controlling the raster settings of the laser apparatus. The raster scan pattern shown in  FIGS. 7A and 7B  are solely shown as an example. In other embodiments, other raster scan patterns having different spacings  718  can be used. As shown, spot areas  714  penetrate a distance  717  within anodized film  702 . Distance  717 , in part, depends on the wavelength of the laser beam. The laser beam should be a wavelength that is tuned to interact with anodized film  702  without substantial interaction with underlying substrate  704 . In some embodiments, a CO 2  laser is used, which produces infrared light having principle wavelength bands centering around 9.4 and 10.6 micrometers. 
     Spot areas  714 , which have been exposed to laser beam pulses, include micro-cracks that can diffusely reflect incident light. To illustrate,  FIG. 7C  illustrates a close-up cross section view of part  700  showing a region around a single spot area  714 . As shown, areas  720  unexposed to the laser beam have standard highly ordered pores  706  as part of a porous metal oxide structure. In contrast, the porous structure within spot area  714  has been modified in the form of cracks  726 . Cracks  726  are formed when energy from the incident laser beam generates enough localized heat that all or some portions of metal oxide material within spot area  714  melt. That is, the heat is sufficient to at least reach the glass transition temperature of the metal oxide material. When the heat dissipates and the metal oxide material cools, the metal oxide material transforms from an amorphous glass-like material to a crystalline form. In this way, the porous structure of the anodized film  702  is transformed to a crystalline metal oxide form in spot areas  714 . In addition, as the metal oxide cools, it contracts and causes cracks  726  to form within spot area  714 . In some embodiments, cracks  714  are on the scale of between about 0.5 and 30 microns in length. Cracks  714  have irregular interfaces that cause incident light to scatter. For example, light ray  722  reflects off of a first surface of cracks  726  at a first angle, while light ray  724  coming in at the same angle as light ray  722  reflects off a second surface of cracks  726  at a second angle different from the first angle. Since cracks  726  have many surfaces arranged at many different angles relative to top surface  710 , different light rays will reflect off cracks  726  at many different angles. In this way, incident visible light can be diffusely reflected off spot areas  714  and impart a white appearance to anodized film  702 . 
       FIG. 8  shows flowchart  800  indicating steps for forming a white anodized film having micro-cracks using a raster scanning pulsed laser beam, in accordance with some embodiments. At  802 , an anodized film having a porous structure is formed on a substrate. As described above, a standard anodized film having a highly ordered porous structure can be used. At  804 , portions of the porous structure are melted using a raster scanning pulsed laser beam. The portions of the porous structure can be arranged in a raster pattern, such as shown in  FIGS. 7A-7C , with each spot area corresponding to a pulse of the laser beam. The laser beam should be tuned such that the energy beam is focused on the anodized film and not on the underlying substrate. At  806 , the melted portions of the porous structure are allowed to cool and contract, thereby forming micro-cracks within the porous structure. During the cooling process all or some of the melted portions can reform into crystalline metal oxide form. The resultant anodized film has micro-cracks that can diffusely reflect incident light, thereby imparting a white and opaque appearance to the anodized film. 
     In some embodiments, a combination of diffuse and specular reflection can be cosmetically beneficial. As described above, specular reflection is when incident light is reflected in substantially one direction, imparting a mirror-like and shiny quality to an object. Specular reflection occurs when incident light reflects off of smooth surfaces such as glass or calm bodies of water. Specular reflection can also make an object appear bright since the light is directly reflected off the smooth surface. Thus, an anodized film that diffusely reflects light, as well as specularly reflects light, can have a white and bright quality. Returning to  FIG. 7C , incident light can specularly reflect off underlying substrate  704  of unexposed areas  720  if the surface of the underlying substrate is smooth. For example, light ray  728  specularly reflects off of underlying substrate  704  of unexposed area  720 . Thus, the relative amount of diffuse and specular reflection of anodized film  702  can be controlled by controlling the relative amount of anodized film  702  exposed to an incident laser beam. The amount of laser beam exposure can be controlled by parameters such as spot density, laser power and spot size. 
       FIGS. 9A-9C  show different laser scan samples illustrating how varying spot density, laser power and spot size can affect the amount of relative diffuse and specular reflection of white anodized films.  FIG. 9A  shows the effect of varying the spot density, or the raster pattern, of a laser beam. The spot density can be measured as a function of spot diameter D. At sample  902 , the distance between the centers of the spots is three times the diameter D of the spots. At sample  904 , the distance between the centers of the spots is two times the diameter D of the spots. At sample  906 , the distance between the centers of the spots is equal to the diameter D of the spots. At sample  908 , the distance between the centers of the spots is half of the diameter D of the spots. The more distance between the spots, the greater specular reflection relative to diffuse reflection. Thus, sample  908  will diffusely reflect more light than sample  902 . Sample  908  will have more of a white matte quality and sample  902  will have more of a reflective mirror-like quality. 
       FIG. 9B  shows the effect of varying the laser power of a laser beam, as indicated by spot darkness. The laser power was varied from low laser power at sample  910  and increased to high laser power at sample  916 . The higher the laser power, the more diffuse reflectance will occur. Thus, sample  916  will have a more matte quality than sample  910 .  FIG. 9C  shows the effect of varying the spot diameters, or laser beam size, of the incident laser beam. Like the sample of  FIG. 9A , samples  918 ,  920 ,  922  and  924  each have different spot densities. However, the spot diameters of these samples are 40% smaller than the spot diameters of  FIG. 9A . Samples  918 ,  920 ,  922  and  924  have different amounts of diffuse versus specular reflective qualities compared to samples  902 ,  904 ,  906  and  908 . 
     The amount of specular reflection of a white anodized film can be measured using any of a number of light reflection measurement techniques. In some embodiments, a spectrometer configured to measure specular light intensity at specified angles can be used. The measure of specular light intensity is associated with an amount of lightness and L value, as described above.  FIG. 9D  shows graph  930  indicating specular reflected light intensity as a function of viewing angle for four different anodized film samples using a spectrometer. Each sample can have a different spot area pattern, such as each of samples  902 - 924  of  FIGS. 9A-9C . Spectra  932 ,  934 ,  936  and  938  are from four different samples of anodized films taken at a 45 degree viewing angle. Spectrum  936  corresponds to a target anodized film sample that has a desired amount of specular reflection for producing a desired white and bright appearance. As shown, spectra  932  and  934  indicate samples that have greater than target amount of specular reflection. Conversely, spectrum  938  indicates a sample that has a lower than target amount of specular reflection. Thus, the spot density, laser power and spot size can be tuned by measuring and comparing the amounts of specular reflection of different samples in order to produce a white anodized film having a desired amount of diffuse and specular reflection. 
       FIG. 10  shows flowchart  1000  indicating steps for tuning a laser cracking process for producing a white anodized film having a target amount of diffuse and specular reflectance. At  1002 , a white anodized film using a laser cracking process is formed. The laser cracking process will have a set of parameters such as spot density, laser power and spot size. At  1004 , the amount of specular reflectance of the white anodized film is measured using a spectrometer. As described above, the spectrometer can measure the spectral reflectance at a defined angle and generate a corresponding spectrum. At  1006 , the specular reflectance spectrum of the white anodized film is compared to a target specular reflectance spectrum. The target specular reflectance spectrum will correspond to a white anodized film having a desired amount of specular and diffuse reflection. 
     At  1008 , it is determined from the comparison whether the amount of specular reflectance of the white anodized film is too high. If the specular reflectance is too high, at  1010 , the relative amount of diffuse reflectance is increased by changing process parameters, such as by increasing the spot density and/or laser power. Then, returning to  1002 , an additional white anodized film is formed using a laser cracking process with the new process parameters. If the specular reflectance is not too high, at  1012 , it is determined from the comparison whether the amount of specular reflectance of the white anodized film is too low. If the specular reflectance is too low, at  1014 , the relative amount of diffuse reflectance is decreased by changing process parameters, such as by decreasing the spot density and/or laser power. Then, returning to  1002 , an additional white anodized film is formed using a laser cracking process with the new process parameters. If the specular reflectance is not too low, the white anodized film has a target amount of diffuse and specular reflectance. 
     In some cases, it can be desirable to produce a white anodized film having both light diffusing irregular pores, as described above with reference to  FIGS. 3-6 , and light diffusing cracks, as described above with reference to  FIGS. 7-10 .  FIG. 11  illustrates a cross section view of part  1100  with anodized film  1102  formed using anodizing techniques in accordance with described embodiments. During an anodizing process, a top portion of metal substrate  1104  is converted to anodized film  1102 . Also during the anodizing process, the current density is varied, or pulsed, with a series of low and high current densities. The pulsed current density during pore formation produces pores  1106  having irregular pore walls  1108 . Irregular pore walls  1108  have multiple tiny surfaces that are arranged a varied angles relative to top surface  1110  that can act as reflection points for diffusing incident light. For example, light ray  1112  reflects off of a first surface of irregular pore walls  1108  at a first angle, while light ray  1113  reflects off a second surface of irregular pore walls  1108  at a second angle different from the first angle. Since irregular pore walls  1108  have many surfaces arranged at many different angles relative to top surface  1110 , different light rays will reflect off irregular pore walls  1108  at many different angles, thereby imparting an opaque and white quality to anodized film  1102 . 
     In addition, after anodized film  1102  having irregular pore walls  1108  is formed, anodized film  1102  has undergone a laser cracking procedure. During the laser cracking procedure, a pulsed laser beam is raster scanned over top surface  1110  of anodized film  1102 . Spot area  1114  represents an area of anodized film  1102  that has been exposed to a pulse from a laser beam during the raster scanning. Spot area  1114  has cracks  1126  that can diffusely reflect incident light. For example, light ray  1122  reflects off of a first surface of cracks  1126  at a first angle, while light ray  1124  reflects off a second surface of cracks  1126  at a second angle different from the first angle. Since cracks  1126  have many surfaces arranged at many different angles relative to top surface  1110 , different light rays will reflect off cracks  1126  at many different angles. In this way, cracks  1126  of spot areas  1114  contribute a cosmetically appealing white and opaque quality to part  1100 . 
       FIG. 12  shows flowchart  1200  indicating steps for forming a white anodized film formed using a combination of varied current density anodizing and laser cracking procedures. At  1202 , an anodized film having irregular pore walls is formed by using a varied current anodizing process. Incident visible light will diffusely reflect off the irregular pore walls and contribute an opaque and white quality to anodized film. At  1204 , cracks are formed within portions of the anodized film using a laser cracking procedure. Incident visible light will diffusely reflect off the cracks and contribute an opaque and white quality to the anodized film. 
     Adding an Underlying Light Diffusing Layer 
     One method for forming a white anodized film involves depositing a layer of white and reflective material below an anodized film such that incident light shining through the anodized layer is diffusely and specularly reflected back through the anodized layer and exits a top surface.  FIGS. 13A-13B  illustrate cross section views of part  1300  undergoing a reflective layer depositing process and an anodizing process in accordance with described embodiments. At  FIG. 13A , aluminum layer  1302  is deposited on metal substrate  1304 . Aluminum layer  1302  can be a substantially pure aluminum layer since pure aluminum is generally brighter in color, i.e., spectrally reflective, compared to aluminum alloys. In some embodiments, aluminum layer  1302  can be deposited using a plating process. In other embodiments, aluminum layer  1302  is deposited using a physical vapor deposition (PVD) process. Aluminum layer  1302  has a first rough surface  1306  that diffusely reflects incident visible light. The PVD process can be tuned to provide the right amount of roughness  1306  to create a target amount diffuse reflection. Aluminum layer  1302 , as viewed from top surface  1308 , can have a silver metallic look of aluminum that has a whitened element from rough surface  1306 . 
     At  FIG. 13B , a portion of aluminum layer  1302  is converted to an aluminum oxide layer  1310 . As shown, a portion  1303  of aluminum layer  1302  remains beneath aluminum oxide layer  1310 . Aluminum portion  1303  has a second rough surface  1307  situated at interface  1316  between aluminum portion  1303  and aluminum oxide layer  1310 . Second rough surface  1307  is associated with and has similar dimensions as first rough surface  1306  prior to anodizing. Thus, second rough surface  1307  can also diffusely reflect light. In some embodiments, aluminum oxide layer  1310  is translucent. Therefore, light incident to top surface  1308  of aluminum oxide layer  1310  can travel through aluminum oxide layer  1310  and diffusely reflect off second rough surface  1307 , imparting a white appearance to part  1300 . For example, light ray  1312  can enter aluminum oxide layer  1310 , reflect off a first surface of rough surface  1306 , and exit aluminum oxide layer  1310  at a first angle. Light ray  1314  can enter aluminum oxide layer  1310  at the same angle as light ray  1312 , reflect off a second surface of rough surface  1306 , and exit aluminum oxide layer  1310  at a second angle different from the first angle. 
     In addition to surface roughness  1306 , light diffusing qualities of aluminum layer  1302  can be enhanced by varying the thickness of aluminum layer  1302 . Specifically, as the thickness of aluminum layer  1302  is increased from 0 microns to 50 microns, the amount of spectral reflection produced by aluminum layer  1302  decreases and the amount of diffuse reflection increases. It is believed that this is due to the rougher surface produced by the thicker sputtered on aluminum material. In general, the longer the sputtering time, the thicker aluminum layer  1302  becomes. As described above, it can be cosmetically beneficial to have a combination of spectral and diffuse reflection in order to provide a white appearing surface that is also bright. In some embodiments, an aluminum layer  1302  having a thickness of ranging from about 10 and 25 microns produces a combination of diffuse and spectral reflection that is cosmetically white and bright. 
       FIG. 14  shows flow chart  1400  indicating steps for forming a white appearing anodized film on a substrate by depositing an underlying reflective layer. At  1402 , an aluminum layer having a sufficiently rough surface to diffusely reflect incident light is deposited on the substrate. In some embodiments, the aluminum layer is substantially pure aluminum. In some embodiments, the aluminum layer is sputtered onto the substrate. The roughness, and therefore the relative amount of diffuse versus spectral reflection, of the surface of the aluminum layer can be tuned by controlling the type of sputtering and thickness of which the aluminum layer is sputtered on. At  1404 , a portion of the aluminum layer is converted to an aluminum oxide layer. Since a portion of the aluminum layer is converted, an underlying portion of the aluminum layer remains beneath the aluminum oxide layer. The underlying portion of the aluminum layer as a second rough surface at the interface between the remaining aluminum layer and the aluminum oxide layer. The second rough surface is associated with the first rough surface of the aluminum layer prior to anodizing. White light entering the aluminum oxide layer can travel through the aluminum oxide layer, diffusely reflect off the second rough surface, and exit the aluminum oxide layer, thereby imparting a white appearance to the substrate. 
     Infusing Light Reflective Particles 
     An additional method for forming a white appearing anodized film involves infusing light reflective white particles within small openings of the anodized film such that the anodized film takes on a white appearance. In some cases, the openings are anodic pores that are naturally formed within the anodized film during the anodizing process. In other cases, the openings are created within the anodized film using, for example, a laser cracking process or a laser drilling process. 
     The light reflective particles can be any suitable particles that have multiple visible light reflecting surfaces for diffusely and specularly reflect substantially all wavelengths of visible light and to give the light reflective particles a white color. In some embodiments, alumina (Al 2 O 3 ) or titania (TiO 2 ), or a combination of alumina and titania, are used. The average size of the light reflective particles can depend partially on the size of the openings in which the light reflective particles are infused within. For example, larger particles may not be able to fit within small opening, in which case, smaller particles are used. The light diffusing particles should also be of a size that optimally diffusely and specularly reflects visible light. In one embodiment using titania particles, an average particle diameter in the range of about 150 to 350 nanometers is used. 
       FIGS. 15A-15C  illustrate cross section views of part  1500  undergoing a pore infusion process, in accordance with some embodiments. At  15 A, part  1500  has undergone an anodizing process to convert a portion of metal substrate  1504  to anodized layer  1502 . Pores  1506  form naturally during the anodizing process in elongated shapes with top ends opened at surface  1510  and bottom ends proximate to underlying substrate  1504 . The average diameter  1508  of pores  1506  for a typical anodizing film ranges from about 10 to 130 nanometers, depending on the electrolyte used. At  15 B, pores  1506  are optionally widened to a larger average diameter  1512 . In some embodiments, pores  1506  are widened to average diameter  1512  of greater than about 100 nanometers, in some cases to around 150 nanometers or more. Any suitable pore widening process can be used. For example, subjecting part  1500  to an acidic solution can widen pores  1506 . 
     At  15 C, pores  1506  are partially or completely filled with light reflective particles  1514 . The infusing of pores  1506  with light reflective particles  1514  can be accomplished using any of a number of suitable techniques. For example, a sedimentation process, a pressing process, an electrophoresis process, or a PVD process can be used, which are described in detail below. After pores  1506  are partially or completely filled, they are optionally sealing using any suitable pore sealing process. Since light reflective particles  1514  are white by diffusely reflecting visible light, they can impart white appearance to anodized layer  1506 . For example, light ray  1516  reflecting off a first surface of light reflective particles  1514  exits at top surface  1510  at a first angle, while light ray  1518  coming in at the same angle as light ray  1516  reflects off a second surface of light reflective particles  1514  and exits at top surface  1510  at a second angle different from the first angle. In addition, any bright specular reflective qualities that light reflective particles  1514  possess are also maintained while within pores  1506 , giving anodized layer  1506  a bright white appearance. 
       FIGS. 16A and 16B  illustrate cross section views of part  1600  undergoing a micro-crack infusion process, in accordance with some embodiments. At  16 A, part  1600  has undergone a laser cracking procedure, such as the laser cracking procedures described above with reference to  FIGS. 7-12 . As shown, pores  1606  of anodized layer  1602 , situated over underlying substrate  1604 , have been modified within spot area  1614 . Spot area  1614  corresponds to an area exposed to a pulse of a laser beam. Micro-cracks  1626  are formed as a result of localized heating from the laser beam and subsequent cooling of the aluminum oxide material within spot area  1614 . In some embodiments, micro-cracks have an average width  1627  ranging from about 100 nanometers to about 600 nanometers. 
     At  FIG. 16B , light reflective particles  1628  are infused within cracks  1626  using any of a number of suitable techniques, such as those described below. Since width of micro-cracks  1626  can be larger than the average diameter of typical pores, the size of light reflective particles  1628  can be larger than those used in the pore infusion embodiment described above with reference to  FIGS. 15A-15C . Light reflective particles  1628  diffusely reflect light, imparting a white appearance to anodized layer  1602 . For example, light rays  1622  and  1624  reflect off a first surface and a second surface, respectively, of light reflective particles  1628  at a first angle and a second angle, respectively. In addition, any bright specular reflective qualities that light reflective particles  1628  possess can contribute a bright specular quality to anodized layer  1606 . 
       FIGS. 17A-17D  illustrate top-down and cross section views of part  1700  undergoing laser drilling and light reflective particle infusion processes, in accordance with some embodiments.  FIG. 17A  shows a top-down view of part  1700  with metal substrate  1704  having undergone a laser drilling process, whereby directing a laser beam at metal substrate  1704  produces an array of holes  1706 . In some embodiments, a pulsed laser system is used where each laser beam pulse corresponds to each hole  1706 . In other embodiments, multiple pulses of a laser beam form each hole  1706 . In some embodiments, a pulsed laser beam is raster scanned over substrate  1704 . Holes  1706  can be arranged in an ordered array, such as shown in  FIG. 17A , or in a random pattern where holes  1706  are randomly distributed within metal substrate  1704 . In some embodiments, holes  1706  have an average diameter  1710  ranging from about 1 micron to about 20 microns. Suitable pitch  1712  between holes  1706  can also be selected. In some embodiments pitch  1712  can be on the scale of average hole diameter  1710 . Any suitable laser of producing a laser beam having a power and wavelength range for drilling holes within metal substrate  1704  can be used.  FIG. 17B  illustrates a close-up cross section view of holes  1706  within metal substrate  1704 . Depth  1714  of openings  1706  can vary depending on particular applications. 
     At  FIG. 17C , part  1700  has undergone an anodizing process whereby a portion of metal substrate  1704  is converted to anodized layer  1702 . In some embodiments, anodized layer  1702  has a thickness  1716  ranging from about 15 microns to about 35 microns, depending on application requirements. As shown, anodized layer  1702  substantially conforms to the shape of metal substrate  1704  such that holes  1706  having a size and a shape appropriate for accommodating light reflective particles exist within anodized layer  1702 . At  FIG. 17D , holes  1706  are partially or completely infused with light reflective particles  1718  using any of a number of suitable techniques, such as those described below. Light reflective particles  1718  diffusely reflect light, imparting a white appearance to anodized layer  1702 . For example, light rays  1720  and  1722  reflect off a first surface and a second surface, respectively, of light reflective particles  1718  at a first angle and a second angle, respectively. In addition, any bright specular reflective qualities that light reflective particles  1718  possess can contribute a bright specular quality to anodized layer  1702 . 
     As described above, a number of suitable techniques can be used to infuse light reflective particles within openings, such as pores, cracks and laser drilled holes, within an anodized film. One technique for infusing light reflective particles within openings of an anodized film involves a sedimentation process, whereby the force of gravity moves the light reflective particles within the openings. The sedimentation technique involves placing the substrate into a slurry containing the light reflective particles. The force of gravity sinks the light reflective particles into the bottom of the openings of the anodized film. The slurry is then heated to allow the liquid portion of the slurry to evaporate, leaving the light reflective particles within the openings. In another variation, prior to exposing the substrate to the slurry, a vacuum desiccator is used to vacuum out air and create a vacuum pressure within the openings where the light reflective particles will be drawn into. 
     Another technique for infusing light reflective particles within openings of an anodized film involves a pressing technique, whereby the light reflective particles are physically forced within the openings. In one embodiment, a substrate is placed into a slurry containing the light reflective particles. A fixture, such as a rubber roller, is then used to press the light reflective particles into the openings of the anodized film. Next, the liquid portion of the slurry is allowed to evaporate, leaving the light reflective particles within the openings. As with the sedimentation technique described above, a vacuum enhanced variation can be applied, whereby the substrate is placed in a vacuum desiccator prior to exposure to the slurry and the pressing operation. 
     An additional technique for infusing light reflective particles within openings of an anodized film involves an electrophoresis technique, whereby the light reflective particles are attracted within the openings by electrophoresis.  FIG. 18  shows electrolytic assembly  1800  illustrating an electrophoresis process whereby a DC voltage is applied across negatively charged cathode  1802  and positively charged anode  1804 , creating an electric field within electrolytic bath  1808 . In this case, cathode  1802  acts as a substrate. Light reflective particles  1806  are added to electrolytic bath  1808  and take on a positive charge, opposite cathode substrate  1802 . As such, light reflective particles  1806  migrate though electrolytic bath  1808  toward cathode substrate  1802  and within any openings within the surface of cathode substrate. When the voltage is removed, the light reflective particles remain within the openings. Note that in other embodiments, the anode can act as the substrate, with negatively charged light particles attracted to the positive anode substrate. In one embodiment, the light reflective particles are titania (TiO 2 ), which can take on a positive charge within an electrolytic solution, and are attracted to a cathode substrate. 
     Another technique for infusing light reflective particles within openings of an anodized film involves a PVD technique, whereby the light reflective particles are sputtered onto the substrate. When the light reflective particles are sputtered onto the substrate, some of the light reflective particles become embedded within the openings. After the PVD process is complete, a separate process for removing excess portions of light reflective material, i.e., material deposited at surface, can be removed, thereby leaving the openings filled with light reflective particles. 
       FIG. 19  shows flowchart  1900  indicating steps for forming a white anodized film by infusing light reflective particles within openings of the anodized film. At  1902 , openings are created within an anodized film. In some embodiments, the openings are the pores that are concurrently formed with growth of the anodized film. In other embodiments, the openings are formed using a separate procedure, such as a laser cracking or a laser drilling procedure. The openings should be sized and shaped suitable for accommodating light reflective particles. At  1904 , light reflective particles are infused within the openings of the anodized film. Any suitable infusion technique can be used. For example, a sedimentation process, a pressing technique, an electrophoresis technique, or a PVD technique described above can be used. 
     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: 20150213
Publication Date: 20190122
Grant Date: 20190122
Priority Date: 20120622
Inventors: BROWNING, LUCY E.
LYNCH, STEPHEN B.
PREST, CHRISTOPHER D.
RUSSELL-CLARKE, Peter N.
TATEBE, MASASHIGE
NASHNER, MICHAEL S.
MCDONALD, Daniel T.
TRYON, BRIAN S.
AKANA, JODY R.
Assignee: APPLE INC
CPC Classifications: [{"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/024", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K26/354", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/355", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24471", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/24471", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/024", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/024", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K26/354", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/355", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/354", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/355", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24471", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/355", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/354", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/024", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/12", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 49769452