Patent ID: 7566499

Claim:
A process for designing optically coherent multilayered film-coated powder, which comprises base particles having thereon at least two coated layers having refractive indexes different from each other, and reflects light with a particular wavelength, the process being characterized by: selecting a substance of the base particles providing an intended function, and an intended color; measuring a spectral intensity curve and values L*0, a*0 and b*0 in CIELAB color system of the intended color; and identifying substances and thicknesses of the coated layers and an order of formation of the layers that provide an optically coherent multilayered film-coated powder having values L*1, a*1 and b*1 that minimize a color difference (ΔZ*) expressed by the following equation (3): ΔZ *=|( L* 0 −L* 1 ) 2 +( a* 0 −a* 1 ) 2 +( b* 0 −b* 1 ) 2 | 1/2 (3) and make a hue ratio expressed by the following equation (4): (a* 0 /b* 0 )/(a* 1 /b* 1 ) (4) within a range of from 0.9 to 1.1, based on the following recurring formula (1) in case where the base particles have a flat plate form: R j + 1 , j = r j + 1 , j + R j , j - 1 ⁢ exp ⁡ ( - 2 ⁢ ⁢ i ⁢ ⁢ δ j ) 1 + r j + 1 , j ⁢ R j , j - 1 ⁢ exp ⁡ ( - 2 ⁢ ⁢ i ⁢ ⁢ δ j ) ⁢ ⁢ 2 ⁢ ⁢ δ j = 4 ⁢ ⁢ π λ ⁢ n j ⁢ d j ⁢ cos ⁢ ⁢ ϕ j ( 1 ) wherein R j+1,j : an amplitude reflection intensity between a j-th layer from the bottom and a layer immediately thereon, j: an integer of at least 1 (j−1=0 represents substance) i: an imaginary unit, r j+1,j : a Fresnel reflection coefficient between a j-th layer from the bottom and a layer immediately thereon, R j,j−1 : an amplitude reflection intensity between a (j−1)-th layer from the bottom and a layer immediately thereon, 2δ j : a phase difference at a j-th layer from the bottom, λ: an intended wavelength of reflected light, n j : a refractive index of the j-th layer from the bottom, d j : a thickness of the j-th layer from the bottom, and φ j : an incident angle of light on the j-th layer from the bottom, and as an equation for compensating a shape of the base particles, based on a visible light reflection waveform obtained by applying a R flat value obtained by substituting the recurring formula (1) to the following equation (2) R ⁡ ( λ ) = ∫ 0 π 2 ⁢ sin ⁢ ⁢ 2 ⁢ θ . · R flat ⁡ ( λ , θ ) · ⁢ ⅆ θ ( 2 ) wherein θ: an incident angle on an outermost layer.