Conductive pigments

• US 5,945,035 A
• Filed: 11/14/1997
• Issued: 08/31/1999
• Est. Priority Date: 11/16/1996
• Status: Expired due to Fees

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Pfaff, Gerhard, Vogt, Reiner
• Primary Examiner(s): KOPEC, MARK T
• Application Number:
  US08/970,351
• Time in Patent Office: 655 Days
• Field of Search: 252/520.1, 252/520.21, 423/71, 423/85, 423/92, 423/275
• US Class Current: 252/520.1
• CPC Class Codes: C01P 2004/20 extending in two dimensions, e.g. plate-like
• CPC Class Codes: C01P 2004/30 extending in three dimensions
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C08K 9/02 Ingredients treated with inorganic substances
• CPC Class Codes: C09C 3/063 Coating
• CPC Class Codes: C09C 3/066 Treatment or coating resulting in a free metal containing surface-region C09C1/0078 takes precedence
• CPC Class Codes: C09D 11/037 characterised by the pigment
• CPC Class Codes: C09D 11/52 Electrically conductive inks
• 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: E04F 15/02 Flooring or floor layers composed of a number of similar elements of webs E04F15/16
• CPC Class Codes: E04F 2290/048 against static electricity
• CPC Class Codes: H01B 1/08 oxides
• CPC Class Codes: H01B 1/20 Conductive material dispersed in non-conductive organic material organic macromolecular compounds or compositions C08

Abstract

The invention relates to electrically conductive pigments which as a conductive layer on a platelet-shaped or needle-shaped substrate have a niobium- and/or tantalum-doped tin oxide or titanium dioxide layer.

Claims

1. A conductive pigment, comprising a platelet-shaped or needle-shaped substrate coated with a conductive layer, wherein the conductive layer is tin oxide doped with niobium and/or tantalum or titanium dioxide doped with niobium- and/or tantalum.

2. A conductive pigment according to claim 1, wherein the content of niobium and/or tantalum in the conductive layer is 0.1-20 atom %.

3. A conductive pigment according to claim 1 wherein the content of doped tin oxide or titanium dioxide relative to the substrate is 25-100% by weight.

4. A conductive pigment according to claim 1 wherein the substrate is platelet-shaped.

5. A conductive pigment according to claim 4, wherein the platelet-shaped substrate is mica, synthetic mica, SiO₂ flakes, TiO₂ flakes, Al₂ O₃ flakes, glass flakes, or a pearl luster pigment.

6. A conductive pigment according to claim 1 wherein the conductive layer is additionally doped with antimony.

7. A conductive pigment according to claim 1 wherein the substrate is a mixture of platelet-shaped and needle-shaped particles or of platelet-shaped and spherical particles.

8. The conductive pigment of claim 1, which is an opaque pigment.

9. The conductive pigment of claim 8, which provides a pale-colored, decorative effect.

10. The conductive pigment of claim 1, wherein the substrate is a pearl luster pigment.

11. The conductive pigment of claim 10, wherein the substrate is mica, optionally coated with a colored or colorless metal oxide.

12. The conductive pigment of claim 1, wherein the pigment has a specific resistance of from 1·

10⁴ to 1·

10⁸ Ω

•

cm.

13. A process for preparing the pigment according to claim 1, which comprises simultaneously combining an aqueous substrate suspension, a hydrolyzable tin salt or titanium salt solution and an aqueous niobium compound and/or tantalum compound, the pH being maintained, by simultaneous addition of a base or an acid, within a range which brings about the hydrolysis of the salts, and a coated substrate resulting therefrom is separated off, washed, dried and calcined at a temperature of from 200-1100°

C. in the absence of oxygen.

14. The process according to claim 13, wherein an aqueous antimony compound is added to the aqueous niobium compound and/or tantalum compound.

15. A varnish, paint, printing ink or plastic composition comprising a conductive pigment according to claim 1.

16. A pigment mixture of 2 or more pigments wherein one pigment is the conductive pigment according to claim 1.