Inorganic effect pigments
An inorganic, non-quarter wave, heterogeneous multilayer effect pigment includes a platy substrate comprising an absorbing optically active metal oxide layer thereon, having an optical thickness from about 20 nm to about 400 nm; a layer of low refractive index material on the absorbing optically active metal oxide layer and having an optical thickness from about 10 nm to about 500 nm; and an outermost optically active layer of a non-absorbing high refractive index material on the low refractive index material and having an optical thickness from about 50 nm to about 1000 nm. The multilayer effect pigment exhibits a blue reflectance ratio (BRR) of at least 3, according to the equation: BRR=(Blue Max)/(Green Min); where Blue Max is the maximum reflectance exhibited over wavelengths 380 nm to 450 nm; and Green Min is the minimum reflectance exhibited over wavelengths 450 nm to 600 nm.
1. An inorganic, non-quarter wave, heterogeneous multilayer effect pigment comprising:
a platy substrate comprising an absorbing optically active metal oxide layer thereon, having an optical thickness from about 20 nm to about 400 nm;
a layer of low refractive index material on the absorbing optically active metal oxide layer and having an optical thickness from about 10 nm to about 500 nm; and
an outermost optically active layer of a non-absorbing high refractive index material on the low refractive index material and having an optical thickness from about 50 nm to about 1000 nm;
wherein:
the multilayer effect pigment has a hue color space of red, fuchsia, and/or magenta color; and the multilayer effect pigment has a chromaticity (15° C.*) of greater than 50 to about 80; the multilayer effect pigment exhibits a blue reflectance ratio (BRR) of at least 3, according to the equation:
BRR=(Blue Max)/(Green Min)
Blue Max is the maximum reflectance exhibited over wavelengths 380 nm to 450 nm; and Green Min is the minimum reflectance exhibited over wavelengths 450 nm to 600 nm,
wherein the Blue Max and Green Min are measured using a Byk Mac Spectrophotometer with D65 illuminant at 15° off specular observation angle.
2. The effect pigment of claim 1 , wherein the platy substrate comprises a synthetic mica, wherein the absorbing optically active metal oxide layer has an optical thickness of from 40 nm to 150 nm, wherein the low refractive index material layer has an optical thickness of from 20 nm to 200 nm, and wherein the non-absorbing high refractive index material layer has an optical thickness of from 60 nm to 150 nm; and
wherein the platy substrate comprises natural mica and/or synthetic mica,
wherein the absorbing optically active metal oxide layer comprises iron oxide,
wherein the low refractive index layer comprises silica; and
wherein the high refractive index layer comprises titania.
3. The effect pigment of claim 2 , wherein the iron oxide layer comprises hematite, magnetite, or maghemite, wherein the silica comprises amorphous silica, wherein the titania comprises anatase, rutile, or a mixture thereof.
4. The effect pigment, of claim 3 , wherein the non-absorbing high refractive index material has a refractive index of n>1.8 and wherein the low refractive index material has a refractive index of n<1.8.
5. The effect pigment of claim 4 , wherein the non-absorbing high refractive index material layer has a refractive index of about 2.00 to about 3.30.
6. The effect pigment of claim 4 , wherein the BRR is from about 3.5 to about 6.
7. The effect pigment of claim 6 , wherein the BRR is about 3.8 to about 5.5.
8. The effect pigment of claim 4 , wherein the effect pigment is free of organic material.
9. The effect pigment of claim 4 , wherein the effect pigment consists of an inorganic substrate and inorganic layers.
10. A product comprising the effect pigment of claim 1 .
11. The product of claim 10 , wherein the product comprises cosmetics, automotive coatings, industrial coatings, inks, and plastics.