OPTICALLY VARIABLE PIGMENTS OF HIGH ELECTRICAL CONDUCTIVITY

• US 20100258769A1
• Filed: 12/11/2008
• Published: 10/14/2010
• 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 8,454,861 B2
• Time in Patent Office: Days
• US Class Current: 252/519.400
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C08K 3/36 Silica
• CPC Class Codes: C08K 9/02 Ingredients treated with inorganic substances
• CPC Class Codes: C09C 1/0015 Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings
• 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: C09C 2200/301 Thickness of the core
• 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

Abstract

The present invention relates to optically variable pigments of high electrical conductivity which comprise a flake-form substrate, which essentially consists of silicon dioxide and/or silicon oxide hydrate, and an electrically conductive layer surrounding the substrate, to a process for the preparation thereof, and to the use of pigments of this type.

Claims

1. Pigments comprising a flake-form substrate, which has at least a thickness of 80 nm and consists of at least 80% by weight, based on the total weight of the substrate, of silicon dioxide and/or silicon oxide hydrate, and an electrically conductive layer surrounding the substrate.

2. Pigments according to claim 1, characterised in that at least one layer package consisting of a dielectric layer having a refractive index n≧

1.8 and a dielectric layer having a refractive index n<

1.8 is located between the substrate and the electrically conductive layer, where the layer having a refractive index n≧

1.8 is located directly on the substrate and optionally on the layer having a refractive index n<

1.8, with the proviso that a layer having a refractive index n<

1.8 is in each case arranged immediately below the electrically conductive layer.

3. Pigments according to claim 1, characterised in that the substrate is an SiO₂ flake.

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

5. Pigments according to claim 4, characterised in that the metal oxide of the conductive layer is tin oxide, zinc oxide, indium oxide and/or titanium oxide.

6. Pigments according to claim 4, 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.

7. Pigments according to claim 2, characterised in that the dielectric layer consists of a material having a refractive index n≧

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

8. Pigments according to claim 2, characterised in that the dielectric layer consists of a material having a refractive index n<

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

9. Pigments according to claim 1, characterised in that the substrate additionally comprises particulate and/or dissolved colorants in a proportion of up to 20% by weight, based on the total weight of the substrate.

10. Process for the preparation of optically variable pigments according to claim 1, comprising the following steps:

a) optionally coating of a flake-form substrate, which has at least a thickness of 80 nm and consists of at least 80% by weight, based on the total weight of the substrate, of silicon dioxide and/or silicon oxide hydrate, with at least one layer package comprising a dielectric layer having a refractive index n≧

1.8 and a dielectric layer having a refractive index n<

1.8, where the layer having a refractive index n≧

1.8 is applied directly to the substrate and optionally additionally to the layer having a refractive index n<

1.8, with the proviso that in each case a layer having a refractive index n<

1.8 is applied immediately below the electrically conductive layer, giving a support flake,

b) coating of the support flake obtained in step a) on all sides with an electrically conductive layer.

11. Process according to claim 10, characterised in that the coating of the flake-form substrate is carried out by the sol-gel process or by wet-chemical methods from inorganic starting materials.

12. Process according to claim 10, characterised in that the electrically conductive layer applied is a layer comprising an antimony-doped tin oxide.

13. A method comprising using pigments according to claim 1 in paints, coatings, printing inks, plastics, in security applications, floorcoverings, films, formulations, ceramic materials, glasses, paper, for laser marking, in heat protection, in dry preparations or in pigment preparations.

14. A method according to claim 13, characterised in that the pigments are employed as a mixture with organic and/or inorganic colorants and/or other electrically conductive materials.