Method of encapsulating pigment flakes with a metal oxide coating

Abstract

A method of encapsulating pigment flakes with a metal oxide coating is provided. According to the method, pigment flakes are mixed with a solvent, a metal salt is added to the solvent, and a reducing agent is added to the solvent, so as to encapsulate the pigment flakes with a metal oxide coating.

1 - 15 . (canceled) 
     
     
         16 . A pigment flake comprising:
 a metal oxide coating,
 wherein the pigment flake is encapsulated with the metal oxide coating by:
 mixing pigment flakes with a solvent; 
 adding a metal salt to the solvent; and 
 adding a reducing agent to the solvent so as to encapsulate the pigment flakes with the metal oxide coating, 
 
 wherein the pigment flakes include the pigment flake, and 
 wherein the metal salt is a precursor to the metal oxide coating. 
   
     
     
         17 . The pigment flake of  claim 16 , wherein the metal oxide coating consists essentially of a metal oxide. 
     
     
         18 . The pigment flake of  claim 16 , wherein the metal salt is a zinc salt. 
     
     
         19 . The pigment flake of  claim 16 , wherein the metal oxide coating is a zinc oxide coating. 
     
     
         20 . The pigment flake of  claim 19 , wherein the zinc oxide coating consists essentially of zinc oxide. 
     
     
         21 . The pigment flake of  claim 16 , wherein the reducing agent is a hydride reducing agent or a borane complex reducing agent. 
     
     
         22 . The pigment flake of  claim 16 , wherein the reducing agent is sodium borohydride. 
     
     
         23 . The pigment flake of  claim 16 , wherein the metal salt dissolves in the solvent to provide metal cations. 
     
     
         24 . The pigment flake of  claim 23 , wherein the reducing agent reduces the metal cations. 
     
     
         25 . The pigment flake of  claim 16 , wherein the metal oxide coating fully encapsulates the pigment flake. 
     
     
         26 . A pigment flake comprising:
 a metal oxide coating that encapsulates the pigment flake,
 wherein the pigment flake is encapsulated with the metal oxide coating by:
 mixing pigment flakes with a solvent; and 
 adding a reducing agent to the solvent so as to encapsulate the pigment flakes with the metal oxide coating, and 
 
 wherein the pigment flakes include the pigment flake. 
   
     
     
         27 . The pigment flake of  claim 26 , wherein the pigment flake further comprises at least one metal layer with at least one exposed surface. 
     
     
         28 . The pigment flake of  claim 26 , wherein the pigment flakes further comprises a metal layer having a top surface, a bottom surface, and at least one side surface. 
     
     
         29 . The pigment flake of  claim 28 , wherein dielectric layers cover the top surface and the bottom surface of the metal layer and not the at least one side surface of the metal layer. 
     
     
         30 . The pigment flake of  claim 28 , wherein the metal layer is formed of aluminum. 
     
     
         31 . The pigment flake of  claim 29 , wherein the dielectric layers are formed of magnesium fluoride. 
     
     
         32 . The pigment flake of  claim 26 , wherein the pigment flakes comprise one of three-layer pigment flakes, five-layer pigment flakes, or seven-layer pigment flakes. 
     
     
         33 . The pigment flake of  claim 26 , wherein one or more of a transition metal salt, a main-group metal salt, or a rare-earth metal salt is a precursor to the metal oxide coating. 
     
     
         34 . The pigment flake of  claim 26 , wherein adding the reducing agent comprises dripping the reducing agent into the solvent. 
     
     
         35 . The pigment flake of  claim 26 , wherein the pigment flake is encapsulated with the metal oxide coating further by:
 washing the pigment flakes with ethanol after adding the reducing agent to the solvent.   
     
     
         36 . An article comprising:
 a pigment flake including a metal layer, a first dielectric layer, and a second dielectric; and   a metal oxide coating that encapsulates the pigment flake,
 wherein the metal oxide coating has a thickness between about 5 nm and about 20 nm. 
   
     
     
         37 . The article of  claim 36 , wherein the metal oxide coating is impermeable to water. 
     
     
         38 . The article of  claim 36 ,
 wherein the pigment flake is encapsulated with the metal oxide coating by:
 mixing pigment flakes with a solvent; and 
 adding a reducing agent to the solvent so as to encapsulate the pigment flakes with the metal oxide coating, and 
   wherein the pigment flakes include the pigment flake.