INTENSELY COLOURED AND/OR OPTICALLY VARIABLE PIGMENTS HAVING AN ELECTRICALLY CONDUCTIVE CORE

• US 20100270510A1
• Filed: 12/11/2008
• Published: 10/28/2010
• Est. Priority Date: 12/19/2007
• Status: Active Grant

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Rueger, Reinhold, Kuntz, Matthias, Krietsch, Burkhard
• Granted Patent: US 8,940,189 B2
• Time in Patent Office: Days
• US Class Current: 252/500
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C08K 3/22 of metals
• CPC Class Codes: C08K 9/02 Ingredients treated with inorganic substances
• CPC Class Codes: C09C 1/0021 comprising a core coated with only one layer having a high or low refractive index
• CPC Class Codes: C09C 1/0024 comprising a stack of coating layers with alternating high and low refractive indices, wherein the first coating layer on the core surface has the high refractive index
• CPC Class Codes: C09C 2200/1004 the core comprising at least one inorganic oxide, e.g. Al2O3, TiO2 or SiO2
• CPC Class Codes: C09D 11/037 characterised by the pigment
• CPC Class Codes: C09D 5/24 Electrically-conducting paints conductive materials H01B1/00
• CPC Class Codes: C09D 5/36 Pearl essence, e.g. coatings containing platelet-like pigments for pearl lustre
• CPC Class Codes: C09D 7/62 modified by treatment with other compounds
• CPC Class Codes: C09D 7/69 Particle size larger than 1000 nm
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

The present invention relates to intensely coloured and/or optically variable pigments which have a flake-form transparent or semitransparent electrically conductive core and at least one colouring dielectric layer surrounding the core, to a process for the preparation of such pigments, and to the use thereof.

Claims

1. Pigments comprising a flake-form transparent or semitransparent electrically conductive core and at least one colouring dielectric layer surrounding the core.

2. Pigments according to claim 1, characterised in that the electrically conductive core has a transparent or semitransparent flake-form substrate and a coating located on all or both sides of the substrate, where the coating has a single- or multilayered structure and at least the outer layer of the coating represents an electrically conductive layer.

3. Pigments according to claim 1, characterised in that the layer surrounding the core is a layer comprising a material having a refractive index n≧

1.8.

4. Pigments according to claim 1, characterised in that the layer surrounding the core is a layer comprising a material having a refractive index n<

1.8.

5. Pigments according to claim 3, characterised in that further colouring layers which surround the respective underlying layer and alternately consist of a material having a refractive index n<

1.8 and a material having a refractive index n≧

1.8 are located on the layer comprising a material having a refractive index n≧

1.8.

6. Pigments according to claim 4, characterised in that further colouring layers which surround the respective underlying layer and alternately consist of a material having a refractive index n≧

1.8 and a material having a refractive index n<

1.8 are located on the layer comprising a material having a refractive index n<

1.8.

7. Pigments according to claim 5, characterised in that a layer comprising a material having a refractive index n≧

1.8 in each case forms the outermost layer of the pigment.

8. Pigments according to claim 2, characterised in that the transparent or semitransparent substrate is selected from the group consisting of synthetic or natural mica, other phyllosilicates, glass flakes, flake-form SiO₂, flake-form Al₂O₃, flake-form TiO₂ and/or synthetic Fe₂O₃ flakes.

9. Pigments according to claim 1, characterised in that the electrically conductive layer comprises one or more doped metal oxides.

10. Pigments according to claim 9, characterised in that the metal oxide of the conductive layer is tin oxide, zinc oxide, indium oxide and/or titanium oxide.

11. Pigments according to claim 9, characterised in that the conductive layer comprising metal oxides is doped with gallium, aluminium, indium, thallium, germanium, tin, phosphorus, arsenic, antimony, selenium, tellurium, molybdenum, tungsten and/or fluorine.

12. Pigments according to claim 3, characterised in that the layer comprising a material having a refractive index n≧

1.8 consists of TiO₂, titanium oxide hydrate, titanium suboxides, Fe₂O₃, FeOOH, SnO₂, ZnO, ZrO₂, Ce₂O₃, CoO, CO₃O₄, V₂O₅, Cr₂O₃ and/or mixed phases thereof.

13. Pigments according to claim 4, characterised in that the layer comprising a material having a refractive index n<

1.8 consists of SiO₂, silicon oxide hydrate, Al₂O₃, aluminium oxide hydrate, mixed phases thereof or MgF₂.

14. Pigments according to claim 1, characterised in that they have intrinsic electrical conductivity.

15. Process for the preparation of intensely coloured and/or optically variable pigments according to claim 1, comprising the following steps:

a) optionally coating of a flake-form transparent or semitransparent substrate with one or more dielectric layers,

b) coating of the substrate on both or all sides with an electrically conductive layer, giving an electrically conductive core,

c) coating of the electrically conductive core on all sides with at least one colouring dielectric layer.

16. Process according to claim 15, characterised in that the coating of the flake-form substrate in steps a), b), and/or c) is carried out by the sol-gel process or by wet-chemical methods from inorganic starting materials.

17. Process according to claim 15, characterised in that the electrically conductive layer is carried out by wet-chemical methods from inorganic starting materials by deposition of a precipitate on the substrate, preventing the formation of a co-precipitate.

18. Process according to claim 15, characterised in that, in step c), a layer system comprising a plurality of colouring dielectric layers lying one above the other, each of which surrounds the underlying layer and which alternately consist of a material having a refractive index n≧

1.8 and a material having a refractive index n<

1.8, is applied, where the first layer surrounding the conductive core may either consist of a material having a refractive index n≧

1.8 or of a material having a refractive index n<

1.8, and the outermost layer of the pigment consists of a material having a refractive index n≧

1.8.

19. Process according to claim 15, characterised in that the layer surrounding the electrically conductive core consists of TiO₂ and/or titanium oxide hydrate.

20. Process according to claim 15, characterised in that the layer surrounding the electrically conductive core consists of SiO₂ and/or silicon oxide hydrate.

21. Process according to claim 15, characterised in that the electrically conductive layer consists of an antimony-doped tin oxide.

22. In a material selected from paint, coating, printing ink, plastic, security product, film, formulation, ceramic material, glass, paper, dry preparations, or pigment preparation, wherein in each case said material contains a pigment, the improvement wherein said pigment is according to claim 1.

23. A material according to claim 22, characterised in that the pigments are employed as a mixture with organic and/or inorganic colorants and/or electrically conductive materials.

24. A material according to claim 22, characterised in that the pigments are employed in security products which are subjected to the influence of an electromagnetic field.

25. Pigment powder comprising pigments according to claim 1, characterised in that the pigment powder is not electrically conductive.