Peg-assisted deposition of crack-free titania nanocrystalline coatings over ai flakes

Abstract

A multi-layered pigment includes a metal core such as Al—SiO 2 . A high refractive index layer such as TiO 2 is applied by an aqueous organic two-phase process to and surrounding the metal core. The high refractive index layer has a thickness greater than 120 nm wherein the high refractive index layer is uniform and crack-free.

We claim: 
     
         1 . A multi-layered pigment comprising:
 a metal core;   a high refractive index layer applied by an aqueous organic two-phase process to and surrounding the metal core, the high refractive index layer having a thickness greater than 120 nm wherein the high refractive index layer is uniform and crack-free.   
     
     
         2 . The multi-layered pigment of  claim 1  wherein the core material is selected from the group consisting of: Al, Cr and Al coated with SiO 2 . 
     
     
         3 . The multi-layered pigment of  claim 1  wherein the high refractive index layer is selected from the group consisting of: TiO 2 , Fe 2 O 4 , Cr 2 O 3 , and Fe 3 O 4    
     
     
         4 . The multi-layered pigment of  claim 3  wherein the high refractive index layer includes TiO 2 . 
     
     
         5 . The multi-layered pigment of  claim 3  wherein the metal core is Al coated with SiO 2 . 
     
     
         6 . A multi-layered pigment comprising:
 an Al—SiO 2  core;   a TiO 2  layer applied by an aqueous organic two-phase process to and surrounding the Al—SiO 2  core, the TiO 2  layer having a thickness greater than 120 nm wherein the TiO 2  layer is uniform and crack-free.   
     
     
         7 . A multi-layered pigment comprising:
 an Al—SiO 2  core;   a TIO 2  layer applied by an aqueous organic two-phase process to and surrounding the Al—SiO 2  core, the TiO 2  layer having a thickness of 160 nm wherein the TiO 2  layer is uniform and crack-free.