Pearlescent Pigment, Process for Producing the Same, Coating Composition and Multilayered Coat

Abstract

This invention relates to a pearlescent pigment, which is composed of flaky alumina substrate particles produced by a hydrothermal process and coat layers formed on the flaky substrate particles and composed of at least one metal oxide including at least a titanium oxide. The metal oxide has an average particle size of from 1 to 500 nm. According to this invention, it is possible to provide a pearlescent pigment, which has wholly uniform photoluminescence and an elegant and silky feel in combination and can fully satisfy artistry as desired.

1 . A pearlescent pigment comprising flaky alumina substrate particles produced by a hydrothermal process and coat layers formed on said flaky substrate particles and composed of at least one metal oxide comprising at least a salt of titanium, wherein said metal oxide has an average particle size of from 1 to 500 nm. 
     
     
         2 . The pearlescent pigment according to  claim 1 , wherein said coat layers of said metal oxide are at least one of mixed layers and stacked layers of two or more metal oxides comprising at least titanium oxide. 
     
     
         3 . The pearlescent pigment according to  claim 1 , wherein said flaky substrate particles have an average particle size of from 0.1 to 50 μm. 
     
     
         4 . The pearlescent pigment according to  claim 1 , wherein said flaky alumina substrate particles have an aspect ratio (particle size/thickness) of from 5 to 500. 
     
     
         5 . The pearlescent pigment according to  claim 1 , wherein said flaky alumina substrate particles have an average particle size a statistical variation coefficient of which is from 20 to 90. 
     
     
         6 . The pearlescent pigment according to  claim 1 , which has an average particle size a statistical variation coefficient of which is from 20 to 90. 
     
     
         7 . A process for the production of a pearlescent pigment, which comprises the steps of:
 dispersing in water flaky alumina substrate particles produced by a hydrothermal process and activated at surfaces thereof by at least one method selected from plasma treatment, ultrasonic treatment, acid treatment, alkali treatment shock treatment and chemical etching treatment,   hydrolyzing in the resulting dispersion a metal salt comprising at least a salt of titanium,   allowing the resulting metal hydroxide or metal oxide to deposit on surfaces of said alumina substrate particles, and then   subjecting the resulting deposit to heat treatment to form, on said surfaces of said alumina substrate particles, metal oxide coat layers having an average particle size of from 1 to 500 nm.   
     
     
         8 . (canceled) 
     
     
         9 . A coating composition comprising a pearlescent pigment according to  claim 1  and a film-forming resin. 
     
     
         10 . The coating composition according to  claim 9 , further comprising a liquid medium. 
     
     
         11 . A multilayered coat comprising a base coat layer formed from a coating composition according to  claim 9  and a clear coat layer formed on said base coat layer. 
     
     
         12 . The multilayered coat according to  claim 11 , which has reflected light intensities having a statistical variation coefficient of not greater than 5 when measured by a photometer. 
     
     
         13 . The multilayered coat according to  claim 11 , which has a 45°/0° reflection intensity ratio of not greater than 100 when measured at an elevation angle of not smaller than 0° by a goniophotometer. 
     
     
         14 . A multilayered coat comprising a colored first base coat layer formed on a surface of a substrate, a second base coat layer formed from a coating composition according to  claim 9  on said colored first base coat layer, and a clear coat layer formed on said second base coat layer. 
     
     
         15 . A multilayered coat comprising a first coat layer formed on a surface of a substrate and at least one second coat layer formed from a coating composition according to  claim 9  on said first coat layer. 
     
     
         16 . A multilayered coat comprising at least two first coat layers formed one over the other on a surface of a substrate and at least one second coat layer formed from a coating composition according to  claim 9  between said at least two first coat layers.