A method to prepare TiO
2-Al
2O
3 doubly coated mica powders has been developed by utilizing homogeneous precipitation method. The laminated structure of Al
2O
3/TiO
2/Mica was confirmed by analyzing the precipitation reaction process and by the surface analysis of the resulting powders with ESCA.
A computor controlled goniospectrophotometer was assembled and the optical properties of the powder surfaces were measured. When Al
2O
3 percentage in coating materials (TiO
2+Al
2O
3) was low, the reflectance around the specular angle was high and the color of reflected light was purplish blue. On the contrary, when the Al
2O
3 percentage reached above 50%, the reflectance decreased in the whole viewing angle range and the color of reflected light came close to achromatic. Thous, the powder surface became to show the appearance of natural luster.
TiO
2-Al
2O
3 doubly coated mica showed higher whiteness than mica itself. In addition, the degree of color darkening by wetting with oil was less than mica.
As a result, it is concluded that TiO
2-Al
2O
3 doubly coated mica has the optical properties fit for cosmetic extender pigment.
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