Patent ID: 7223799

Claim:
A color-developing composition, wherein said color-developing composition comprises a powder dispersion containing a liquid phase and a solid phase; wherein said solid phase comprises a spherical silica powder; wherein said liquid phase has a refractive index of n 1 and said solid phase containing said silica has a refractive index of n 2 ; wherein the mean particle size of the silica powder is about 0.1 μm to 200 μm; wherein said spherical silica powder containing solid phase has a refractive index of 1.3<n 2 <2.0; and wherein said refractive index of said liquid phase is within 0.05 of said refractive index of said solid phase, which satisfies Equation (1): |n 1 −n 2 |<0.05 (1); whereby a color is developed at the interface between said liquid phase and said solid phase in said color-developing composition when said solid phase is mixed with or dispersed in said liquid phase.