Transparent conductive pigments

• US 20050253117A1
• Filed: 05/17/2005
• Published: 11/17/2005
• Est. Priority Date: 05/17/2004
• Status: Active Grant

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Rueger, Reinhold, Ott, Frank, Pfaff, Gerhard, Stahlecker, Otto
• Granted Patent: US 7,416,688 B2
• Time in Patent Office: Days
• US Class Current: 252/500
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/40 Electric properties
• 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 2200/1004 the core comprising at least one inorganic oxide, e.g. Al2O3, TiO2 or SiO2
• CPC Class Codes: C09C 2200/102 the core consisting of glass or silicate material like mica or clays, e.g. kaolin
• CPC Class Codes: C09C 2220/10 Wet methods, e.g. co-precipitation
• CPC Class Codes: H01B 1/08 oxides

Abstract

Disclosed are transparent conductive pigments of flake-form substrates coated with a conductive layer, where the number-weighted mean particle area F₅₀ of the transparent conductive pigments is greater than or equal to 150 μm², and processes for the production of the pigments, and the use thereof.

Claims

1. Transparent conductive pigments comprising flake-form substrates coated with a conductive layer, wherein the number-weighted mean particle area F₅₀ of the transparent conductive pigments is greater than or equal to 150 m².

2. Transparent conductive pigments according to claim 1, wherein the number-weighted mean particle area F₅₀ of the transparent conductive pigments is greater than or equal to 200 μ

m².

3. Transparent conductive pigments according to claim 1, wherein the proportion of pigments having a particle area of less than 80 μ

m² is less than or equal to 33%, based on the transparent conductive pigments.

4. Transparent conductive pigments according to claim 1, wherein the proportion of pigments having a particle area of less than 40 μ

m² is less than or equal to 15% by weight, based on the transparent conductive pigments.

5. Transparent conductive pigments according to claim 1, wherein the flake-form substrates are flake-form TiO₂, synthetic or natural mica, phyllosilicates, glass flakes, flake-form SiO₂ and/or flake-form Al₂O₃.

6. Transparent conductive pigments according to claim 1, wherein the conductive layer comprises one or more doped metal oxides.

7. Transparent conductive pigments according to claim 6, wherein the metal oxide of the conductive layer is tin oxide, zinc oxide, indium oxide and/or titanium oxide.

8. Transparent conductive pigments according to claim 6, wherein the conductive layer comprising metal oxides is doped with gallium, aluminium, indium, thallium, germanium, tin, phosphorus, arsenic, antimony, selenium, tellurium and/or fluorine.

9. Transparent conductive pigments according to claim 1, wherein one or more layers comprising metal oxides, metal oxide hydrates, metal suboxides, metal fluorides, metal nitrides, metal oxynitrides or a mixture thereof are located above and/or below the conductive layer.

10. A process for preparing transparent conductive pigments according to claim 1, comprising coating flake-form substrates with a conductive layer, and reducing the proportion of flake-form substrates or transparent conductive pigments having a particle area of less than 150 μ

m², before and/or after the coating with a conductive layer, such that the number-weighted mean particle area F₅₀ of the transparent conductive pigments is greater than or equal to 150 μ

m².

11. A process according to claim 10, wherein reducing the proportion of flake-form substrates or transparent conductive pigments is carried out by sedimentation, decantation, air classification and/or sieving.

12. A process according to claim 10, wherein coating the flake-form substrates with a conductive layer is carried out by a wet-chemical method.

13. A process according to claim 10, further comprising applying one or more layers comprising metal oxides, metal oxide hydrates, metal suboxides, metal fluorides, metal nitrides, metal oxynitrides or a mixture thereof before and/or after coating the flake-form substrates with a conductive layer.

14. A process according to claim 13, wherein applying the one or more layers is carried out by a wet-chemical method, by a sol-gel process or by a CVD and/or PVD process.

15. A paint, coating, printing ink, plastic article, a security application, floorcovering, film, formulation, ceramic material, glass article, paper, laser marking, heat protection material, dry preparation or pigment composition comprising pigments according to claim 1.

16. A paint, coating, printing ink, plastic article, a security application, floorcovering, film, formulation, ceramic material, glass article, paper, laser marking, heat protection material, dry preparation or pigment composition wherein the pigments are in a mixture with organic and/or inorganic colorants and/or conductive materials.