Patent ID: 7951420

Claim:
A method of preparing a pigment exhibiting a color-shifting effect, said pigment comprising a base material, a first layer, a second layer, a third layer, and optionally an outer protective layer, said base material being a mica, said first layer and said third layer each independently comprising a metal oxide having a high refractive index, said second layer comprising a metal oxide having a low refractive index, and said base material being coated with said first layer, said second layer, said third layer, and optionally said outer protective layer, and the method comprising the steps of: (i) heating mica powder suspension in water; followed by, (ii) adjusting the pH value of the mixture to between 2 and 9 by adding a diluted aqueous hydrochloric acid solution or a diluted aqueous sodium hydroxide solution; followed by, (iii) adding a first inorganic salt solution; followed by, (iv) maintaining the pH value of the mixture constant by adding a diluted aqueous hydrochloric acid solution or a diluted aqueous sodium hydroxide solution; followed by, (v) stiffing the mixture at constant temperature; (vi) adjusting the pH value of the mixture to between 6 and 14 by adding a diluted aqueous sodium hydroxide solution and stirring the mixture for a period of time; followed by, (vii) adding a second inorganic salt solution; followed by, (viii) maintaining the pH value of the mixture constant by adding a diluted aqueous hydrochloric acid solution; followed by, (ix) stiffing the mixture at constant temperature; followed by, (x) adjusting the pH value of the mixture to between 2 and 9 by adding a diluted aqueous hydrochloric acid solution or a diluted aqueous sodium hydroxide solution and stirring the mixture for a period of time; followed by, (xi) adding a first inorganic salt solution; followed by, (xii) maintaining the pH value of the mixture constant by adding a diluted aqueous hydrochloric acid solution or a diluted aqueous sodium hydroxide solution; and followed by, (xiii) stiffing the mixture at constant temperature.