Abstract:
A method for providing a protective coating and enhanced optical qualities to a gemstone. The method includes coating a first portion and a second portion of a gemstone with TiO 2  doped with calcium oxide (TiO 2 +). The TiO 2 + coated gemstone is next coated with a diamond like carbon (DLC) coating. The gemstone may be synthetic or natural. The composite gemstone, having been coated with both TiO 2  and DLC, exhibits high refractivity and enhanced wear resistance and color.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to gemstones and more specifically it relates to a method for producing a highly refractive composite gemstone having a protective coating and other enhanced optical qualities. 
     2. Description of Related Art 
     Gemstones may be found in nature or they may be man-made, and they include but are not limited to naturally occurring rubies, sapphires, emeralds, and diamonds as well as man-made cubic zirconium and moissanite stones. Gemstones are typically cut to a desired shape and are often placed within a metal setting for use as a ring or other common pieces of jewelry. 
     One problem with gemstones is that they often do not have the desired optical beauty or the desired color grade. Another problem is that they can become scratched or worn over time thereby reducing their attractiveness. 
     In these respects, the highly refractive composite gemstones made according to the embodiments of the present invention substantially depart from conventional concepts and designs of the prior art, and in so doing provide gemstones having substantially enhanced optical qualities and a protective coating to reduce scratching or wear on their surfaces. 
     BRIEF SUMMARY OF THE INVENTION 
     The embodiments of the present invention provide a new highly refractive composite gemstone having a protective coating and enhanced optical qualities, and a method for producing such a composite gemstone. 
     The present invention generally comprises first coating the entire surface of the gemstone with a highly refractive layer of TiO 2  containing or doped with calcium oxide in the ratio of about 3.5 to about 4.5 TiO 2 :about 1 calcium oxide as measured by x-ray photoelectron spectroscopy (XPS) analysis, hereinafter referred to as “TiO 2 +”, to substantially improve the glossiness or luster of the stone. Most preferably the ratio is about 3.75 TiO 2 :about 1 calcium oxide. TiO 2 + has been found to be particularly effective for this purpose as it has a greater refractive index than even diamond. 
     The TiO 2 + layer is then sealed in by coating the entire surface of the TiO 2 + coated gemstone with an additional layer of diamond-like carbon (“DLC”). The DLC coating enhances the wear resistance and color of the resultant composite gemstone. 
     There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and that will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting. 
     To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific method and construction illustrated and described within the scope of the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various other objects, features, and attendant advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
         FIG. 1  is a flowchart of a preferred embodiment of the inventive method. 
         FIG. 2  is a side view of a non-coated gemstone. 
         FIG. 3  is a side view of the gemstone with a first portion coated with TiO 2 +. 
         FIG. 4  is a side view of a gemstone with a first portion and second portion coated with TiO 2 +. 
         FIG. 5  is a side view of the gemstone of  FIG. 4  with the first portion additionally coated with DLC. 
         FIG. 6  is a side view of the gemstone of  FIG. 4  with the first portion and second portion additionally coated with DLC to form a composite gemstone. 
         FIG. 7  is a side sectional view of the composite gemstone of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views,  FIG. 1  illustrates a method for producing a composite gemstone  10 , which in the first instance comprises coating a first portion  24  and a second portion  22  of a gemstone  20  with a layer of TiO 2 + as shown in  FIGS. 2 ,  3 , and  4 . The gemstone  20  may be synthetic or natural. The TiO 2 + coating is highly refractive and greatly enhances the optical characteristics, particularly glossiness or luster of the underlying gemstone  20 . 
       FIG. 1  shows schematically the desired process for coating a gemstone  20  with TiO 2 +. TiO 2 + provides a highly refractive coating which is in fact more refractive than diamond. Physical Vapor Deposition is an acceptable coating process for TiO 2 +, and encompasses sputtering, cathodic arc, and other coating procedures known to those skilled in the art that may be utilized with the present invention to achieve similar results. 
       FIG. 2  illustrates an exemplary gemstone  20  having a solid exterior surface. It can be appreciated that the gemstone  20  may be pre-cut to have various sizes, shapes, and structure which are commonly utilized within the jewelry industry, other than the specific example illustrated in the attached drawings. The gemstone  20  may be any one of various gemstones including synthetic or natural, such as but not limited to naturally occurring diamonds, rubies, sapphires, emeralds, and man-made stones such as cubic zirconium and moissanite. 
     Utilizing a conventional Physical Vapor Deposition application process such as sputtering or cathodic arc, the first portion  24  of the gemstone  20  is preferably coated with a first layer  30  of TiO 2 + as shown in  FIG. 3  of the drawings. The first portion  24  may represent the broad upper portion of the gemstone  20  (if applicable) or the lower tapering portion of the gemstone  20  (if applicable). The first layer  30  comprising TiO 2 + may vary in thickness as desired depending upon the gemstone and the application for which the gemstone is to be utilized, but a preferred range of thickness of about 100 to 300 nanometers, and a most preferred thickness of about 150 nanometers has been found useful for jewelry applications. 
     After the first layer  30  has been applied to the gemstone, the second portion  22  of the gemstone  20  is then coated with a second layer  40  of TiO 2 + thereby providing the TiO 2 + coating about the entire exterior surface of the gemstone  20  as shown in  FIGS. 4 and 7  of the drawings. 
     The thickness of the second layer  40  may vary as desired depending upon the gemstone  20  and the application for which the gemstone is to be utilized. The second layer  40  of TiO 2 + may be thinner or thicker than first layer  30  of TiO 2 +, but again a thickness of about 200 to about 300 nanometers, and a most preferred thickness of about 150 nanometers has been found useful for jewelry application. In addition, the second layer  40  and the first layer  30  may each have varying thickness throughout as desired. The inventor has found however that a uniform thickness of TiO 2 + throughout is optimal for each layer  30 ,  40  for jewelry applications. 
     Alternatively, the first layer  30  and the second layer  40  may be applied simultaneously upon the gemstone  20 . In another alternative embodiment, only a portion of the gemstone  20  may be covered with the TiO 2 + coating. 
     The TiO 2 + coating upon the gemstone  20  preferably covers the entire exterior surface of the gemstone  20  for providing enhanced optical characteristics, particularly, high light refraction. TiO 2 + coatings have a high refractive index which increases the overall refraction of the gemstone  20 . 
     Turning now to  FIGS. 4 and 5 , there is illustrated the next part of the method of the embodiments of the invention which comprises coating the first portion  24  and the second portion  22  of the gemstone  20  with a diamond-like carbon (DLC) coating applied over the previously applied TiO 2 + highly refractive coating. A preferred form of DLC for the purpose is tetrahedral amorphous carbon (TaC). The DLC coating enhances the wear resistance and color characteristics of the underlying gemstone  20 . Additionally, when used to coat cubic zirconium, DLC prevents the cloudiness that often develops in cubic zirconium over time as a result of absorption of water and CO 2 . 
       FIG. 1  also shows schematically the desired process for coating a gemstone  20  with DLC after it has been coated with TiO 2 , to provide the resultant composite gemstone embodiments of the invention. DLC provides a hard, transparent and wear resistant coating. U.S. Pat. No. 5,879,775 discloses an acceptable Physical Vapor Deposition coating process and structure utilizing DLC and is hereby incorporated by reference for describing how to utilize DLC. There will be apparent to those skilled in the art various other DLC coating procedures and compositions that may be utilized with the present invention to achieve similar results. 
     Utilizing a conventional DLC application process, the first TiO 2 + coated portion  24  of gemstone  20  is now preferably coated with a first layer  50  of DLC as shown in  FIG. 5  of the drawings. The first portion  24  may represent the broad upper portion of the gemstone  20  (if applicable) or the lower tapering portion of the gemstone  20  (if applicable). The first layer  50  comprising DLC may vary in thickness as desired depending upon the gemstone  20  and the application for which the gemstone is to be utilized, but a preferred range of thickness of about 100 to 300 nanometers, and a most preferred thickness of about 150 nanometers has been found useful for jewelry applications. 
     After the first layer  50  has been applied to the gemstone  20  and hardened, the second TiO 2 + coated portion  22  of the gemstone  20  is then coated with a second layer  60  of DLC thereby providing the DLC coating about the entire TiO 2 + coated exterior surface of the gemstone  20  as shown in  FIGS. 6 and 7  of the drawings. 
     The thickness of the second layer  60  may vary as desired depending upon the gemstone  20  and the application for which the gemstone is to be utilized. The second layer  60  of DLC may be thinner or thicker than first layer  50  of DLC, but again a thickness of about 100 to about 300 nanometers, and most preferred thickness of about 150 nanometers has been found useful for jewelry applications. In addition, the second layer  60  and the first layer  50  may each have varying thickness throughout as desired. The inventor has found that a uniform thickness throughout is optimal for each layer  50 ,  60  for jewelry applications. 
     Alternatively, the first layer  50  and the second layer  60  may be applied simultaneously upon the TiO 2 + coated gemstone  20 . In another alternative embodiment, only a portion of the gemstone may be covered with the DLC coating. 
     The DLC coating upon the gemstone  20  preferably covers the entire TiO 2 + coated exterior surface of the gemstone  20  for providing enhanced optical characteristics such as but not limited to improved color grade. The inventor has discovered during testing that by coating the TiO 2 + coated gemstone  20  with a DLC coating, that the gemstone  20  is diluted by the DLC optics thereby improving the overall apparent color grade of the gemstone  20 . In addition, the DLC coating about the TiO 2 + coated gemstone  20  provides increased wear resistance to scratching and other damaging events. The inventor has found that by coating the TiO 2 + coated gemstone  20  with the DLC coating that the hardness of the gemstone  20  is increased by at least 0.50 Mohs. The inventor has also found that the best results occur when the gemstone  20  is comprised of a transparent media such as, but not limited, to diamond. 
     With respect to the above description then, it is to be realized that all equivalent method steps and structural variations and relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. 
     Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the embodiments invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.