Abstract:
Metallization is disposed on at least a portion of an electrically nonconductive substrate. Plating is then disposed on the metallization, and an anodized layer of the plating is configured to provide the substrate with an anodized surface. The substrate may be glass or ceramic, and in particular sapphire. The substrate may be optically transmissive, and the metallization and plating may define a window adapted to transmit light through the substrate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application relates to and claims the benefit of prior U.S. Provisional Application No. 60/436,436 entitled Inorganic Coating filed Dec. 24, 2002 and incorporated by reference herein. 

   BACKGROUND OF THE INVENTION 
   Anodizing is an electrochemical process which grows a dense oxide layer on certain metals, including aluminum, niobium, tantalum, titanium and tungsten. The thickness of this layer and its properties vary greatly depending on the metal. For example, the anodizing process converts an aluminum surface into an extremely hard, durable, corrosion resistant, long-lasting aluminum oxide, which has diverse and important applications. Further, this surface can be processed to have a variety of colors as well as finishes, such as reflective or matte. 
   SUMMARY OF THE INVENTION 
   Applications, such as those involving high definition television (HDTV), lasers and high-power illumination are problematic for some component parts and associated coatings, particularly those coatings colored with organic materials or dyes. Such organic coatings can easily be destroyed, damaged or degraded by resulting high temperatures associated with these applications. By comparison, anodizing provides an inorganic coating that can withstand high temperatures without degradation. Conventional anodization, however, is limited to certain metals. Anodizing of electrically non-conductive materials, such as glass or ceramic, advantageously provides an inorganic coating suitable for high temperature applications on the surface of materials readily adapted to a wide range of both optical and non-optical applications. 
   One aspect of an anodized apparatus comprises an electrically nonconductive substrate, a metallization disposed on at least a portion of the substrate, a plating disposed on the metallization, and an anodized layer of the plating configured to provide the substrate with an anodized surface. In one embodiment, the substrate is glass or ceramic, and in a particular embodiment, the substrate is sapphire. In another embodiment, the substrate is optically transmissive, and the metallization and plating define a window adapted to transmit light through the substrate. In a particular embodiment, the anodized layer has a matte black finish. In yet another embodiment, the metallization comprises an adhesion layer disposed on at least a portion of the substrate and a diffusion barrier disposed on the adhesion layer. In a particular embodiment, the plating is aluminum, the adhesion layer is chromium and the diffusion barrier is nickel. 
   An aspect of an anodizing method comprises the steps of providing an electrically nonconductive substrate, depositing a metallization on at least a portion of the substrate, depositing a plating on the metallization and anodizing the plating. The anodizing method may comprise a further step of defining an aperture with the metallization and the plating, where the aperture provides a window for transmitting light through the substrate. Coloring a surface of the plating and finishing the surface may be additional steps. In one embodiment, the providing a substrate step comprises the substep of adapting the substrate as an optical component. In another embodiment, the metallization step comprises the substeps of depositing an adhesion layer on at least a portion of the substrate and depositing a diffusion barrier on the adhesion layer. The adhesion layer step may comprise the substep of sputtering chromium onto the substrate. The diffusion barrier step may comprise the substep of sputtering nickel onto the chromium. A further step may include sputtering gold onto the nickel. Yet another step may comprise masking the substrate so as to form an unmetallized area. The plating step may comprise the substep of electroplating aluminum onto the metallization. 
   Another aspect of an anodized apparatus comprises a substrate means for transmitting light, a plating means for anodization, and a metallization means disposed on the substrate means for adhering the plating means to the substrate means. In one embodiment, the apparatus further comprises an anodized layer means anodized from the plating means for absorbing light and withstanding high temperatures without degradation. There may also be a window means for transmitting light through the substrate, which is defined by the plating means and the metallization means, where the anodized layer means is disposed around the window means. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of an anodized electrically non-conductive substrate; 
       FIG. 2  is a flow diagram of an anodizing process for an electrically non-conductive substrate; 
       FIG. 3  is an exploded perspective view of a metallization; and 
       FIGS. 4A-B  are perspective and detailed perspective views, respectively, of a plating. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates an anodized electrically non-conductive substrate  10  having a blank substrate  100 , a metallization  300  and a plating  400 . Advantageously, the blank substrate  100  need not be aluminum or metal in order to be anodized and achieve the hard, durable finish associated with anodization. The blank substrate  100  has a surface to be anodized  101 , including an anodized area  110  and, optionally, a non-anodized area  120 . In one particularly useful embodiment, the blank substrate  100  is transparent or translucent so that the non-anodized area  120  provides a window or lens that transmits light and so that the anodized area  110  blocks, absorbs and/or reflects light. As such, the anodized substrate  10  can be used in optical or opto-electrical applications, where the anodized coating is capable of withstanding high temperatures without degradation. 
   Further shown in  FIG. 1 , the metallization  300  has a metallized area  310  corresponding to the anodized area  110  and an unmetallized area  320  defining an aperture and corresponding to the non-anodized area  120 . Similarly, the plating  400  has a plated area  410  corresponding to the anodized area  110  and an unplated area  420  defining an aperture and corresponding to the non-anodized area  120 . An anodizing process for electrically non-conductive material is described with respect to  FIG. 2 , below. The metallization  300  is described in detail with respect to  FIG. 3 , below. The plating  400  is described in detail with respect to  FIG. 4 , below. 
     FIG. 2  illustrates an anodization process  200  having the steps of providing a substrate  210 , metallizing the substrate surface  220 , plating the metallized surface  230 , and anodizing the plated surface  240 . With respect to the providing a substrate step  210 , the substrate is an electrically non-conductive material as distinguished from the metals conventionally associated with anodization. In one embodiment, the substrate  100  ( FIG. 1 ) is any of various glass or ceramic materials having transparent, translucent or opaque characteristics. In a particularly advantageous embodiment, the substrate is sapphire, which can be optically transmissive and can provide superior high temperature characteristics as compared to glass. 
   As shown in  FIG. 2 , the metallizing step  220  utilizes a thin-film process to apply the metallization  300  ( FIG. 3 ) to the blank substrate  100 . The metallization  300  ( FIG. 3 ) advantageously allows the plating  400  ( FIG. 4A ) to be disposed on a variety of substrate materials, as described above. Metallizing  220  has the substeps of depositing an adhesion layer  330  ( FIG. 3 ), depositing a diffusion barrier  340  ( FIG. 3 ) and depositing an optional layer  350  ( FIG. 3 ). If the anodized substrate  10  ( FIG. 1 ) is to have a non-anodized area  120  ( FIG. 1 ), then a masking or etching substep is applied before or after the depositing substeps. The plating step  230  provides a coating of “anodizable” metal over the metallization  300  ( FIG. 3 ). It is this plating  400  ( FIG. 4A ) that advantageously provides a surface that allows the anodizing step  240 . Metallizing  220  is described in detail with respect to  FIG. 3 , below. The plating  230  and anodizing  240  are described in detail with respect to  FIGS. 4A-B , below. 
     FIG. 3  illustrates a metallization  300  having a metallized area  310  and an optional unmetallized area  320 , as described above. The metallization  300  also has an adhesion layer  330 , a diffusion barrier  340  and an optional layer  350 , as described below. In one embodiment, the adhesion layer  330  is Cr, Ti, W, Ti/W, or Ni/V having a thickness up to about 3,500 Å. In one embodiment, Ti, W or Ti/W are used on most ceramics, including sapphire, Cr is used on all glass materials, and Ni/V is used for both glass and ceramics. The end results are approximately the same for these metals/alloys in terms of adhesion and subsequent processing. In one embodiment, the diffusion barrier  340  is Ni having a thickness up to about 10,000 Å. In one embodiment, the optional layer  350  is Au having a thickness up to about 4,000 Å. 
   As shown in  FIG. 3 , the metallization  300  is applied to the blank substrate  100  ( FIG. 1 ) using any of three thin film technologies, including sputtering, chemical vapor deposition (CVD) or vacuum evaporation, although the integrity of the metallization adhesion to the substrate can be lower with CVD and evaporation than that achieved by sputtering. In a particular embodiment, an RF sputter is used with the process parameters set forth in Table 1, below. 
   
     
       
             
           
             
             
           
         
             
               TABLE 1 
             
             
                 
             
             
               Metallization Process Parameters 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               Hi Vacuum System 
               Minimum vacuum level 7 × 10 −7  torr- 
             
             
                 
               the lower the better. 
             
             
               Process Atmosphere 
               Argon (99.999%) at chamber pressure of 
             
             
                 
               between 10-12 millitorr 
             
             
               RF Sputter 
               500 W for each of Cr (99.99%); Ni 
             
             
                 
               (99.995%), Au (99.99%) 
             
             
               Process Time 
               Cr: 5-10 minutes @ 300-350 Å/min. 
             
             
                 
               Ni: 10-20 minutes @ 400-500 Å/min. 
             
             
                 
               Au: 2-4 minutes @ 1000 Å/min. 
             
             
               Target-to-substrate distance 
               3.5-4.0 inches 
             
             
               Reflectance power 
               At or near 0 W during all runs and constantly 
             
             
                 
               adjusted if needed. 
             
             
               Other: 
               Ensure that substrate does not overheat. 
             
             
                 
               Ensure that the chamber pressure is 
             
             
                 
               maintained between 10-12 millitorr during 
             
             
                 
               sputtering 
             
             
                 
             
           
        
       
     
   
     FIGS. 4A-B  illustrate a plating  400  having a plated area  410  and an optional unplated area  420 , as described above. As shown in  FIG. 4B , the plating  400  also has an unanodized layer  430 , an anodized layer  440 , and an anodized surface  450 , as described below. The plating  400  is applied to the metallization  300  ( FIG. 3 ), as described below, so as to provide an anodized surface  450  for electrically non-conductive materials. The plating thickness is configured to be as thin as possible so as to be most compatible with high temperature applications, yet configured to have sufficient thickness for the anodization process, which converts portions of the plated layer  400  to the anodized layer  440 , with the unanodized layer  430  remaining. The plating may be any metal that can be anodized, such as those listed above. In one embodiment, the plating  400  is Al or Ti, either having a thickness up to about 0.002 inches. 
   Further shown in  FIG. 4B , for Al, the plating  400  is applied by an electro-plating process, a sputtering process, or a combination of electro-plating and sputtering, which are well-known processes in the art. In an alternative embodiment, the plating  400  is applied by chemical vapor deposition (CVD), plasma coating, vacuum evaporation or other vacuum coating technique in lieu of sputtering, although the adhesion strength to the metallization  300  ( FIG. 3 ) will be lower. For Ti, the plating  400  is applied by sputtering, CVD, plasma coating, vacuum evaporation or other vacuum coating technique. For Ti, however, advantageously there is no need for metallization  300  ( FIG. 3 ) or the metallizing process  220  ( FIG. 2 ) prior to the plating process  230  ( FIG. 2 ). Unlike Al, Ti has sufficient adherence to glass, ceramic or other electrically nonconductive substrates for the plating  400  to be deposited directly onto the substrate  100  ( FIG. 1 ). 
   In a particular embodiment, the plated layer  220  is electro-plated aluminum, which can be applied by a vendor such as Alumiplate, Inc., Minneapolis, Minn. The anodized surface  450  can be given a matte or reflective finish by pre-treatment with etching or smoothing solutions, respectively. The anodized surface  450  can also be colored either integrally with the anodizing process or by electrolytic immersion in a metal salt. In a particular embodiment, the anodized surface  450  is colored black. 
   Although an anodized apparatus and anodizing method are described above with respect to a generally flat substrate, the term substrate is intended to denote materials, components and assemblies having any shape or size. Further, although metallization and plating are described above as being applied on an apparently outside or exposed surface of a substrate, the anodizing method is applicable to inside or unexposed surfaces of components or assembles. In addition, although specific mention is made of glass and ceramic materials, the anodizing method is applicable to polymers and other electrically non-conductive materials as well as metals and metal alloys not conventionally associated with anodization. 
   An anodized apparatus and an anodizing method have been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in art will appreciate many variations and modifications.