Interference pigments on the basis of silicon oxides
The present invention relates to pigments, the particles of which generally have a length of from 2 μm to 5 mm, a width of from 2 μm to 2 mm, and a thickness of from 20 nm to 2 μm, and a ratio of length to thickness of at least 2:1, wherein the particles contain a core of SiO 2 or a silicon/silicon oxide obtained by heating SiO y flakes with 1.1≦y≦1.8 in an oxygen-free atmosphere at a temperature of at least 400° C., which core has a narrow distribution of particle sizes and two substantially parallel faces, the distance between which is the shortest axis of the core, and a material layer having a high index of refraction a metal oxide; 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, the particles of which have a length of from 2 μm to 5 mm, a width of from 2 μm to 2 mm, and a ratio of length to thickness of at least 2:1, wherein the particles consist of a core of SiO 2 or a silicon/silicon oxide obtained by heating SiO y flakes with 1.1≦y≦1.8 in an oxygen-free atmosphere at a temperature of at least 400° C., which core has a thickness of from 20 to 200 nm, a defined thickness in the range of 30% of the average thickness, high plane-parallelism and two substantially parallel faces, the distance between which is the shortest axis of the core;
and
a material layer having a high index of refraction; and
optionally an additional layer or layers, which layer or layers consist of a material selected from a dielectric material having a high index of refraction, a dielectric material having a low index of refraction, one or more inorganic colorant, one or more organic colorant and mixtures thereof, which pigment particle may also have a surface treatment.
2. A pigment according to claim 1 , wherein the thickness of the particle core is from 50 to 150.
3. A pigment according to claim 1 , wherein the dielectric material having a high index of refraction is one or more compounds selected from the group consisting of ZnS, ZnO, ZrO 2 , TiO 2 , carbon, In 2 O 3 , indium tin oxide, Ta 2 O 5 , Cr 2 O 3 , CeO 2 , Y 2 O 3 , Eu 2 O 3 , Fe 3 O 4 , Fe 2 O 3 , HfN, HfC, HfO 2 , La 2 O 3 , MgO, Nd 2 O 3 , Pr 6 O 11 , Sm 2 O 3 , Sb 2 O 3 , SiO, Se 2 O 3 , SnO 2 and WO3.
4. A pigment according to claim 1 , wherein the material having a high index of refraction is a metal oxide.
5. A pigment according to claim 1 , wherein the dielectric material having a high refractive index is one or more compounds selected from the group consisting of TiO 2 , ZrO 2 , Fe 2 O 3 , Fe 3 O 4 , Cr 2 O 3 , ZnO, an iron titanate, an iron oxide hydrate and a titanium suboxide, or a mixed phase of these compounds.
6. Paints, printing inks, textiles, coatings, plastics, cosmetics, glazes for ceramics and glass, which are comprising a pigment according to claim 1 .
7. A pigment, the particles of which have a length of from 2 μm to 5 mm, a width of from 2 μm to 2 mm, and a ratio of length to thickness of at least 2:1, wherein the particles consist of a core of SiO 2 obtained by heating SiO y flakes with 1.1≦y≦1.8 in an oxygen containing gas at a temperature of at least 200° C. or a silicon/silicon oxide obtained by heating SiO y flakes with 1.1≦y≦1.8 in an oxygen-free atmosphere at a temperature of at least 400° C., wherein the SiO y flakes with 1.1≦y≦1.8 have a thickness of from 20 to 200 nm and a defined thickness in the range of 30% of the average thickness, which core has a thickness of from 20 to 200 nm, high plane-parallelism and two substantially parallel faces, the distance between which is the shortest axis of the core;
and
a material layer having a high index of refraction; and
optionally an additional layer or layers, which layer or layers consist of a material selected from a dielectric material having a high index of refraction, a dielectric material having a low index of refraction, one or more inorganic colorant, one or more organic colorant and mixtures thereof, which pigment particle may also have a surface treatment.
8. A pigment according to claim 7 , wherein the thickness of the particle core is from 50 to 150.
9. A pigment according to claim 7 , wherein the dielectric material having a high index of refraction is one or more compounds selected from the group consisting of ZnS, ZnO, ZrO 2 , TiO 2 , carbon, In 2 O 3 , indium tin oxide, Ta 2 O 5 , Cr 2 O 3 , CeO 2 , Y 2 O 3 , Eu 2 O 3 , Fe 3 O 4 , Fe 2 O 3 , HfN, HfC, HfO 2 , La 2 O 3 , MgO, Nd 2 O 3 , Pr 6 O 11 , Sm 2 O 3 , Sb 2 O 3 , SiO, Se 2 O 3 , SnO 2 and WO 3 .
10. A pigment according to claim 7 , wherein the material having a high index of refraction is a metal oxide.
11. A pigment according to claim 7 , wherein the dielectric material having a high refractive index is one or more compounds selected from the group consisting of TiO 2 , ZrO 2 , Fe 2 O 3 , Fe 3 O 4 , Cr 2 O 3 , ZnO, an iron titanate, an iron oxide hydrate and a titanium suboxide, or a mixed phase of these compounds.
12. Paints, printing inks, textiles, coatings, plastics, cosmetics, glazes for ceramics and glass, which are comprising a pigment according to claim 7 .