Interference Pigments on the Basis of Glass Flakes
The present invention relates to pigments, comprising a plate-like substrate of glass having an average thickness of <1 μm, especially of from 20 nm to 400 nm, and (a) a dielectric material, especially a metal oxide, having a high index of refraction; or (a) a metal layer, especially a thin semi-transparent metal layer; a process for their production and their use in paints, ink-jet printing, for dyeing textiles, for pigmenting coatings (paints), printing inks, plastics, cosmetics, glazes for ceramics and glass.
1 . A pigment, comprising a plate-like substrate of glass having an average thickness of <1 μm, and
(a) a dielectric material, having a high index of refraction; or
(a) a thin semi-transparent metal layer.
2 . A pigment according to claim 1 , wherein the glass substrate consists of ECR glass.
3 . The pigment according to claim 1 , wherein the pigment comprises in addition (b) a metal oxide of low refractive index, wherein the difference of the refractive indices is at least 0.1.
4 . The pigment according to claim 3 , wherein the metal oxide of high refractive index is TiO 2 , ZrO 2 , Fe 2 O 3 , Fe 3 O 4 , Cr 2 O 3 , ZnO or a mixture of these oxides or an iron titanate, an iron oxide hydrate, a titanium suboxide or a mixture and/or mixed phase of these compounds.
5 . The pigment according to claim 3 , wherein the metal oxide of low index of refraction is SiO 2 , Al 2 O 3 , AlOOH, B 2 O 3 , or a mixture thereof, wherein alkali or earth alkali metal oxides can be contained as additional component.
6 . The pigment according to claim 1 , wherein the glass core has an average thickness of from 20 to 220 nm.
7 . The pigment according to claim 1 , comprising a mixed layer of Al 2 O 3 /TiO 2 , or MgO/TiO 2 , or a dielectric layer/a metal layer/a dielectric layer.
8 . The pigment according to claim 1 , wherein the glass flakes have a homogenous coating of a metal oxide of high refractive index, and a large Gaussian thickness distribution of the glass flakes.
9 . A process for producing the interference pigment according to claim 1 , by coating glass flakes with one or more metal oxides in a wet process by hydrolysis of the corresponding water-soluble metal compounds, by separating, drying and optionally calcinating the pigment thus obtained, or
by suspending glass flakes in an aqueous and/or organic solvent containing medium in the presence of a metal compound and depositing the metal compound onto glass flakes by addition of a reducing agent.
10 . (canceled)
11 . Paints, printing inks, plastics, cosmetics, ceramics and glass, which are pigmented with a pigment according to claim 1 .
12 . A pigment, according to claim 1 comprising a plate-like substrate of glass having an average thickness of from 20 nm to 400 nm, and
(a) a metal oxide, having a high index of refraction; or
(a) a thin semi-transparent metal layer.
13 . A pigment according to claim 12 , wherein the glass substrate consists of ECR glass.
14 . The pigment according to claim 2 , wherein the pigment comprises in addition (b) a metal oxide of low refractive index, wherein the difference of the refractive indices is at least 0.1.
15 . The pigment according to claim 14 , wherein the metal oxide of high refractive index is TiO 2 , ZrO 2 , Fe 2 O 3 , Fe 3 O 4 , Cr 2 O 3 , ZnO or a mixture of these oxides or an iron titanate, an iron oxide hydrate, a titanium suboxide or a mixture and/or mixed phase of these compounds.
16 . The pigment according to claim 4 , wherein the metal oxide of low index of refraction is SiO 2 , Al 2 O 3 , AlOOH, B 2 O 3 , or a mixture thereof, wherein alkali or earth alkali metal oxides can be contained as additional component.
17 . The pigment according to claim 1 , wherein the glass core has an average thickness of from 50 to 220 nm.
18 . The pigment according to claim 2 , comprising a mixed layer of Al 2 O 3 /TiO 2 , or MgO/TiO 2 , or a dielectric layer/a metal layer/a dielectric layer.
19 . The pigment according to claim 2 , wherein the glass flakes have a homogenous coating of a metal oxide of high refractive index, and a large Gaussian thickness distribution of the glass flakes.
20 . The pigment according to claim 19 wherein the metal oxide of high refractive index is TiO 2 .