Interference pigments

Abstract

The present invention relates to interference pigments based on transparent, low-refractive-index, flake-form substrates which have a high-refractive-index coating consisting of TiO.sub.2 having a layer thickness of 20-200 nm and optionally an outer protective layer, and to the use thereof in paints, coatings, printing inks, security printing inks, plastics, button pastes, ceramic materials, glasses, for seed coloring, as dopants in the laser marking of plastics and papers, as additive for the laser welding of plastics, as additive for coloring in the foods and pharmaceuticals sectors, and in cosmetic formulations and for the preparation of pigment compositions and dry preparations.

Claims

1. An interference pigment, which consists of a low-refractive-index, transparent, flake substrate having only one high-refractive-index coating consisting essentially of TiO.sub.2 having a layer thickness of 70-160 nm and optionally further coated with an outer protective layer, wherein the pigment exhibits a color flop from the short wave color green at a steep viewing angle to the long wave color red at a flat viewing angle, wherein the substrate has an average thickness of 0.2 to 0.8 m and a size in the other two dimensions of between 5 and 60 m, wherein the standard deviation of the thickness of the substrate flakes is 15%, based on their average thickness, and wherein the TiO.sub.2 is in the rutile modification and optionally contains an amount of tin oxide sufficient to provide it in the rutile modification.

2. An interference pigment according to claim 1, wherein the standard deviation of the thickness of the flake substrate is 10%, based on their average thickness.

3. An interference pigment according to claim 1, wherein the transparent flake is an SiO.sub.2 flake, Al.sub.2O.sub.3 flake, natural or synthetic mica flake or a glass flake.

4. An interference pigment according to claim 3, wherein the transparent flake is an SiO.sub.2 flake.

5. A process for the production of the interference pigment of claim 1, comprising, coating the substrate by a wet-chemical method by hydrolytic decomposition of a titanium metal salt in aqueous medium or by thermal decomposition by a CVD or PVD process.

6. A pigment composition comprising one or more binders, optionally one or more additives and one or more interference pigments according to claim 1.

7. A dry preparation in the form of pellets, granules, chips, or briquettes, comprising one or more interference pigments according to claim 1.

8. The interference pigment of claim 1, wherein the substrate has a refractive index of 1.8.

9. A paint, button paste, coating, printing ink, security printing ink, plastic, ceramic material, glass, seed coating, dopant for the laser marking of plastics and papers, additive for the laser welding of plastics, additive for food or pharmaceutical coloring, or cosmetic, which comprises an interference pigment of claim 1.

10. The interference pigment of claim 1, wherein the pigment has no outer protective layer.

11. The interference pigment of claim 1, wherein the pigment has an outer protective layer.

12. An interference pigment, which consists of a low-refractive-index, transparent, SiO.sub.2 flake substrate having only one high-refractive-index coating consisting essentially of TiO.sub.2 having a layer thickness of 20-200 nm and optionally further coated with an outer protective layer, wherein the pigment exhibits a color flop from green at a steep viewing angle to red at a flat viewing angle, wherein the substrate has an average thickness of 0.1 to 1 m and a size in the other two dimensions of between 5 and 60 m, wherein the standard deviation of the thickness of the substrate flakes is 15%, based on their average thickness, and wherein the TiO.sub.2 is in the rutile modification and optionally contains an amount of tin oxide sufficient to provide it in the rutile modification.

13. An interference pigment according to claim 1, wherein the thickness of the high-refractive-index coating is matched to the average thickness of the flake substrate.

14. The interference pigment of claim 12, wherein the high-refractive-index coating consisting essentially of TiO.sub.2 has a layer thickness of 50 to 180 nm.

15. The interference pigment of claim 12, wherein the high-refractive-index coating consisting essentially of TiO.sub.2 has a layer thickness of 70 to 160 nm.

16. The pigment composition of claim 6, which comprises at least one additive selected from absorbents, astringents, antimicrobial substances, antioxidants, antiperspirants, antifoaming agents, antidandruff active ingredients, antistatics, biological additives, bleaching agents, chelating agents, deodorants, emollients, emulsifiers, emulsion stabilisers, dyes, humectants, film formers, odour substances, flavour substances, insect repellents, preservatives, anticorrosion agents, cosmetic oils, solvents, oxidants, vegetable constituents, buffer substances, reducing agents, surfactants, propellent gases, opacifiers, UV filters, UV absorbers, denaturing agents, viscosity regulators, perfumes and vitamins.

17. An interference pigment, which consists of a low-refractive-index, transparent, SiO.sub.2 flake substrate having only one high-refractive-index coating consisting essentially of TiO.sub.2 having a layer thickness of 70-160 nm and optionally further coated with an outer protective layer, wherein the pigment exhibits a color flop from the short wave color green at a steep viewing angle to the long wave color red at a flat viewing angle, wherein the substrate has an average thickness of 0.2 to 0.8 m and a size in the other two dimensions of between 5 and 60 m, wherein the standard deviation of the thickness of the substrate flakes is 10%, based on their average thickness, wherein the thickness of the high-refractive-index coating is matched to the average thickness of the flake substrate, and wherein the TiO.sub.2 is in the rutile modification and optionally contains an amount of tin oxide sufficient to provide it in the rutile modification.

Description

EXAMPLES

Example 1: Interference Pigment with Color Travel from Intense Green to Red

(1) 100 g of SiO.sub.2 flakes (particle size 5-50 m, average thickness 450 nm, standard deviation of the thickness: about 5%) are suspended in 2 l of deionised water and heated to 80 C. with vigorous stirring. A solution of 12 g of SnCl.sub.45H.sub.2O and 40 ml of hydrochloric acid (37%) in 360 ml of deionised water is metered into this mixture at pH 1.6. An amount of 460 ml of TiCl.sub.4 solution (400 g of TiCl.sub.4/I) is subsequently metered in at a pH of 1.6. The pH is kept constant during the addition of both the SnCl.sub.45H.sub.2O solution and TiCl.sub.4 solutions using NaOH solution (32%). The pH is subsequently adjusted to 5.0 using sodium hydroxide solution (32%), and the mixture is stirred for a further 15 minutes.

(2) For work-up, the pigment is filtered off, washed with 20 l of deionised water, dried at 110 C. and calcined at 850 C. for 30 min., giving an interference pigment having an intense, bright-green color, strong luster and high transparency. On changing to flat viewing angles, the pigment exhibits a red interference color.

USE EXAMPLES

Example A: Shower Gel

(3) Phase A

(4) TABLE-US-00001 Raw material Source INCI [%] Pigment from Example 1 Merck KGaA 0.10 Keltrol T Kelco Xanthan Gum 0.75 Water, demineralised Aqua (Water) 64.95
Phase B

(5) TABLE-US-00002 Raw material Source INCI [%] Plantacare Cognis GmbH Decyl Glucoside 20.00 2000 UP Texapon Cognis GmbH Sodium Laureth Sulfate, 3.60 ASV 50 Sodium Laureth-8 Sulfate, Magnesium Laureth Sulfate, Magnesium Laureth-8 Sulfate, Sodium Oleth Sulfate, Magnesium Oleth Sulfate Bronidox L Cognis GmbH Propylene Glycol, 5-Bromo-5- 0.20 Nitro-1,3-Dioxane Everest 79658 Haarmann & Parfum 0.05 SB perfume oil Reimer GmbH (deleted) 1% FD&C Blue BASF AG Aqua (Water), CI 42090 0.20 No. 1 in water (FD&C Blue No. 1)
Phase C

(6) TABLE-US-00003 Raw material Source INCI [%] Citric acid monohydrate Merck KGaA/Rona Citric Acid 0.15 Water, demineralised Aqua (Water) 10.00
Preparation:

(7) For phase A, stir the interference pigment into the water. Slowly scatter in the Keltrol T with stirring and stir until it has dissolved. Add phases B and C one after the other while stirring slowly until everything is homogeneously distributed. Adjust pH to 6.0 to 6.4.

Example B: Nail Varnish

(8) TABLE-US-00004 Raw material Source INCI [%] Pigment from Merck KGaA 2.00 Example 1 Thixotropic International Toluene, Ethyl Acetate, Butyl 98.00 nail varnish Lacquers S.A. Acetate, Nitrocellulose, base 1348 Tosylamide/Formaldehyde Resin, Dibutyl Phthalate, Isopropyl Alcohol, Stearalkonium Hectorite, Camphor, Acrylates Copolymer, Benzophenone-1
Preparation:

(9) The interference pigment is weighed out together with the varnish base, mixed well manually using a spatula and subsequently stirred at 1000 rpm for 10 min.

Example C: Surface Coating System

(10) 90% by weight of Hydroglasur BG/S colorless (water-borne varnish from Ernst Diegel GmbH)

(11) 10% by weight of green interference pigment from Example 1

(12) Coating by spraying at 80 C.

(13) 5 min predrying at 80 C.

(14) 20 min baking at 180 C.

Example D: Plastic

(15) 1 kg of polystyrene granules is wetted uniformly with 5 g of adhesive in a tumble mixer. 42 g of green interference pigment from Example 1 are then added and mixed for 2 minutes. These granules are converted into stepped plates having the dimensions 430.5 cm under conventional conditions in an injection-moulding machine. The stepped plates are distinguished by their pronounced sparkle effect.

Example E: Coloring of Confectionery

(16) Crude product: effervescent sweets white

(17) Spray solution:

(18) 94% of alcoholic shellac solution from Kaul

(19) 6% of green interference pigment from Example 1

(20) The effervescent sweets are sprayed with an interference pigment/shellac solution until the desired color application has been reached. Subsequent drying with cold air is possible.

(21) The entire disclosures of all applications, patents and publications, cited herein and of corresponding German application Nos. 10 2004 05 2544.7, filed Oct. 28, 2004 and 10 2004 006 360.5 filed Feb. 9, 2004, is incorporated by reference herein.

(22) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(23) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.