Interference pigments

Abstract

The present invention relates to interference pigments based on transparent, low-refractive-index, flake-form substrates which have a high-refractive-index coating consisting of TiO 2 having a layer thickness of 20-200 nm and optionally an outer protective layer, and to the use thereof in paints, coatings, printing inks, security printing inks, plastics, button pastes, ceramic materials, glasses, for seed coloring, as dopants in the laser marking of plastics and papers, as additive for the laser welding of plastics, as additive for coloring in the foods and pharmaceuticals sectors, and in cosmetic formulations and for the preparation of pigment compositions and dry preparations.

1 . An interference pigment comprising a low-refractive-index, transparent, flake substrate coated with a high-refractive-index coating consisting essentially of TiO 2  having a layer thickness of 20-200 nm and optionally further coated with an outer protective layer.  
     
     
         2 . The interference pigment of  claim 1 , wherein the standard deviation of the thickness of the substrate flakes is ≦15%, based on their average thickness.  
     
     
         3 . The interference pigment of  claim 2 , wherein the transparent flake substrate is an SiO 2  flake, Al 2 O 3  flake, synthetic mica flake or a glass flake.  
     
     
         4 . The interference pigment of  claim 1 , wherein the transparent flake substrate is an SiO 2  flake.  
     
     
         5 . The interference pigment of  claim 1 , wherein the TiO 2  is in the rutile modification and optionally contains a small amount of tin oxide for rutilization.  
     
     
         6 . The interference pigment of  claim 1 , which consists of the substrate, the high-refractive-index coating consisting essentially of TiO 2  and, optionally, the outer protective layer.  
     
     
         7 . The intererence pigment of  claim 1 , wherein the high-refractive-index coating consisting essentially of TiO 2  has a layer thickness of 50 to 180 μm.  
     
     
         8 . The interference pigment of  claim 1 , wherein the substrate has an average thickness of 0.02 to 2 μm.  
     
     
         9 . The interference pigment of  claim 1 , wherein the substrate has an average thickness of 0.1 to 1.0 μm.  
     
     
         10 . The interference pigment of  claim 2 , wherein the substrate has a refractive index of ≦1.8.  
     
     
         11 . The interference pigment of  claim 1 , wherein the pigment exhibits a green interference color.  
     
     
         12 . The interference pigment of  claim 11 , which has a strong color shift from green at a steep viewing angle to red at a flat viewing angle.  
     
     
         13 . A process for the production of an interference pigments according to  claim 1 , which comprises coating the substrate by a wet-chemical method by hydrolytic decomposition of a titanium metal salt in aqueous medium or by thermal decomposition by a CVD or PVD process.  
     
     
         14 . A paint, button paste, coating, printing ink, security printing ink, plastic, ceramic material, glass, seed coating, dopant for the laser marking of plastics and papers, additive for the laser welding of plastics, additive for food or pharmaceutical coloring, or cosmetic, which comprises an interference pigment of  claim 1 .  
     
     
         15 . A pigment composition comprising one or more binders, optionally one or more additives and one or more interference pigments according to  claim 1 .  
     
     
         16 . A dry composition in the form of pellets, granules, chips, or briquettes, comprising one or more interference pigments according to  claim 1.