Electrically conductive pigment
The present invention relates to electrically conductive pigments, to a process for the preparation thereof and to the use thereof, in particular in antistatic or dissipative articles or surfaces, for example in paints, coatings, printing inks or floorcoverings.
1. Electrically conductive pigments, comprising a dielectric flake-form substrate and an electrically conductive layer surrounding the substrate, which has a volume average particle size d 95 <25 μm and a ratio of a volume average particle size d 95 to a volume average size of the pigments d 5 is greater than 5, and wherein at least 5 percent by volume of a powder bed of the electrically conductive pigments have a nominal particle size of <5 μm.
2. Electrically conductive pigments according to claim 1 , wherein the substrate is selected from the group consisting of natural mica flakes, synthetic mica flakes, talc flakes, kaolin flakes, sericite flakes, aluminium oxide flakes, silicon dioxide flakes, glass flakes of mixtures of two or more thereof.
3. Electrically conductive pigments according to claim 1 , wherein the electrically conductive layer consists of one or more doped metal oxides.
4. Electrically conductive pigments according to claim 3 , wherein the doped metal oxide is tin oxide, zinc oxide, indium oxide and/or titanium oxide which is doped with gallium, aluminium, indium, thallium, germanium, tin, phosphorus, arsenic, antimony, selenium, tellurium, molybdenum, tungsten and/or fluorine.
5. Electrically conductive pigments according to claim 3 , wherein the electrically conductive layer consists of a doped tin oxide.
6. Electrically conductive pigments according to claim 3 , wherein the electrically conductive layer consists of antimony-doped tin oxide, wherein the antimony content is 5 to 15 mol % based on the total amount of antimony oxide and tin oxide.
7. Electrically conductive pigments according to claim 1 , wherein at least one dielectric layer is located between the flake-form substrate and the electrically conductive layer.
8. Electrically conductive pigments according to claim 1 , wherein the ratio of the volume average particle size d 95 to the volume average size of the pigments d 5 is greater than 7.
9. Electrically conductive pigments according to claim 1 , wherein the pigment has a volume average particle size d 95 of <15 μm.
10. A process for preparing electrically conductive pigments according to claim 1 , comprising coating a powder comprising dielectric flake-form substrates which has a volume average particle size d 95 <25 μm and in which at least 5 percent by volume of the powder have a particle size <5 μm in an aqueous suspension
optionally with one or more dielectric layers, and finally
with an electrically conductive layer.
11. The process according to claim 10 , wherein the dielectric substrates are natural mica flakes, synthetic mica flakes, talc flakes, kaolin flakes, sericite flakes, aluminium oxide flakes, silicon dioxide flakes, glass flakes or mixtures of two or more thereof.
12. The process according to claim 10 , wherein the powder comprising dielectric flake-form substrates is coated with an electrically conductive layer comprising one or more doped metal oxides.
13. A product selected from the group consisting of paints, coatings, printing inks, plastics, coating compositions, sensors, security applications, far laser marking, floor coverings, films, ceramic materials, glasses and papers, comprising electrically conductive pigments according to claim 1 .
14. The product according to claim 13 , which is selected from the group consisting of paints, coatings, printing inks, plastics, coating compositions, floor coverings, films and ceramic materials, and having a pigment mass concentration of 25 to 60%.
15. Electrically conductive pigments according to claim 1 , which have a surface resistance value of 10E+04 ohm or less when measured in a coating having a layer thickness of 15 to 20 μm on a plastic part at a pigment mass concentration of 35 to 45%.
16. Electrically conductive pigments according to claim 1 , wherein the ratio of the volume average particle size d 95 to a volume average size of the pigments d 5 is greater than 5 and up to 15.
17. Electrically conductive pigments according to claim 16 , wherein the pigment has a volume average particle size d 95 of <15 μm.
18. Electrically conductive pigments according to claim 16 , wherein the electrically conductive layer consists of antimony-doped tin oxide, wherein the antimony content is 5 to 15 mol % based on the total amount of antimony oxide and tin oxide.
19. Electrically conductive pigments according to claim 16 , which have a surface resistance value of 10E+04 ohm or less when measured in a coating having a layer thickness of 15 to 20 μm on a plastic part at a pigment mass concentration of 35 to 45%.
20. Electrically conductive pigments according to claim 1 , wherein the ratio of the volume average particle size d 95 to a volume average size of the pigments d 5 is 7 to 11.