PVD-metallic effect pigments with diffractive structure and metal nanoparticles, process for preparing them and use thereof
The invention relates to metallic effect pigment, the metallic effect pigment having at least one diffractive structure and at least one layer which comprises metal nanoparticles and metal oxide phase, the metal of the metal oxide phase and the metal of the metal nanoparticles in this at least one layer being identical. The invention further relates to a process for preparing these metallic effect pigments, to a coating composition, and to a coated article.
1. A metallic effect pigment consisting of
(a) a single layer which comprises metal nanoparticles and a metal oxide phase, the metal of the metal oxide phase and the metal of the metal nanoparticles being identical in the layer, wherein the layer has a diffractive structure and wherein the layer has a first outer face and a second outer face, the amount of metal nanoparticles in the first outer face differs from the amount of metal in the second outer face by at least 10 atom % or
(b) two layers disposed one atop the other, with at least one layer comprising metal nanoparticles in a metal oxide phase, and the metal of the metal oxide phase and the metal of the metal nanoparticles being identical in the at least one layer, wherein the at least one layer has a first outer face and a second outer face, the amount of metal nanoparticles in the first outer face differs from the amount of metal in the second outer face by at least 10 atom %, and wherein the two layers have a diffractive structure wherein the metallic effect pigment exhibits an optical rainbow effect from diffraction of incident light at the diffractive structure.
2. The metallic effect pigment of claim 1 , wherein the metal of the at least one layer which comprises metal nanoparticles and metal oxide phase is selected from the group consisting of aluminum, magnesium, chromium, silver, copper, gold, zinc, tin, manganese, iron, cobalt, nickel, titanium, tantalum, molybdenum, tungsten, mixtures thereof, and alloys thereof.
3. The metallic effect pigment of claim 1 , wherein the average size of the metal nanoparticles is in a range from 1 to 50 nm.
4. The metallic effect pigment of claim 1 , wherein in the at least one layer which comprises metal nanoparticles and metal oxide phase, the average content of metal M and oxygen is at least 80 atom%, based on this one layer.
5. The metallic effect pigment of claim 1 , wherein the at least one diffractive structure has at least one periodic pattern with diffractive elements.
6. The metallic effect pigment of claim 5 , wherein the periodic pattern has 5000 to 20,000 diffractive elements/cm.
7. The metallic effect pigment of claim 1 , wherein the diffractive structure has a depth of at least 40 nm.
8. The metallic effect pigment of claim 1 , wherein an average layer thickness of the at least one layer which comprises metal nanoparticles and metal oxide phase is in a range from 8 to 500 nm.
9. The metallic effect pigment of claim 1 , wherein the amount of metal nanoparticles changes continuously over the thickness of the at least one layer which comprises metal nanoparticles and metal oxide phase.
10. The metallic effect pigment of claim 9 , wherein the amount of metal nanoparticles changes at least partly with a gradient of 0.1 to 4 atom%/nm over the thickness of the at least one layer which comprises metal nanoparticles and metal oxide phase.
11. The metallic effect pigment of claim 1 , wherein the amount of metal nanoparticles changes discontinuously between two successive layers.
12. The metallic effect pigment of claim 1 , wherein the metal is a trivalent metal and the metallic effect pigment has at least one first and one second successive layer, the first layer comprising metal nanoparticles and the second layer comprising elemental metal, the amount of metal nanoparticles in the outer face of the first layer, which comprises metal nanoparticles and metal oxide phase, being in a range from 1 to 50 atom%, and the amount of elemental metal in the outer face of the second layer being in a range from 60 to 95 atom%, with the proviso that the difference in the amount of metal nanoparticles and of elemental metal in the two outer faces is at least 10 atom%.
13. The metallic effect pigment of claim 1 , wherein the metal is a tetravalent metal and the metallic effect pigment has at least one first and one second successive layer, the first layer comprising metal nanoparticles and the second layer comprising elemental metal, the amount of metal nanoparticles in the outer face of the first layer, which comprises metal nanoparticles and metal oxide phase, being in a range from 1 to 50 atom%, and the amount of elemental metal in the outer face of the second layer being in a range from 60 to 95 atom%, with the proviso that the difference in the amount of metal nanoparticles and of elemental metal in the two outer faces is at least 10 atom%.
14. The metallic effect pigment of claim 1 , wherein the at least one layer which comprises metal nanoparticles and metal oxide phase has an average oxygen content of 30 to 77 atom%, based on the total amount of metal and oxygen in this layer.
15. A coating composition comprising the metallic effect pigment of claim 1 .
16. An article provided with the metallic effect pigment of claim 1 .
17. The metallic effect pigment of claim 5 , wherein the at least one diffractive structure has at least one periodic pattern with diffractive elements comprising geometric shapes or bodies.
18. The metallic effect pigment of claim 1 , wherein the diffractive structure is selected from the group consisting of symmetrical triangles, asymmetrical triangles, grooves, rectangles, circles, wavy lines, cones, truncated cones, knobs, prisms, pyramids, truncated pyramids, cylinders, hemispheres, and combinations thereof.
19. The metallic effect pigment of claim 1 , wherein the metallic effect pigment further comprises smooth sections present on the metallic effect pigment surface.
20. The metallic effect pigment of claim 1 , wherein at least one outer face has a depth of approximately 10 nm.
21. The metallic effect pigment of claim 1 , wherein the layer or layers further comprise extraneous elements selected from the group consisting of one or more of nitrogen, sulfur, carbon, hydrogen.
22. A coated article coated with a coating composition comprising the metallic effect pigment of claim 1 .
23. The metallic effect pigment of claim 1 , wherein the metal of the at least one layer which comprises metal nanoparticles and metal oxide phase is selected from the group consisting of aluminum, chromium, titanium, tantalum, mixtures thereof; and alloys thereof.
24. The metallic effect pigment of claim 1 , wherein the average size of the metal nanoparticles is in a range from 1 to 10 nm.
25. A process for preparing the metallic effect pigment of claim 1 , comprising:
(a1) applying a release layer to a linearly movable substrate,
(a2) introducing a diffractive structure into the release layer, preferably by embossing, and
(a3) applying at least one metal to the release layer on the linearly movable substrate, in a vacuum chamber having a vapor-deposition section, by means of reactive physical vapor deposition (PVD), in the presence of oxygen,
or
(b1) applying a release layer to a linearly movable substrate,
(b2) applying at least one metal to the release layer on the linearly movable substrate, in a vacuum chamber having a vapor-deposition section, by means of reactive physical vapor deposition (PVD), in the presence of oxygen, and
(b3) introducing a diffractive structure onto and/or into at least one surface of the PVD layer applied in step (b2), preferably by embossing,
and also
c) detaching the applied PVD layer(s) provided with a diffractive structure,
d) comminuting the detached PVD layer(s),
e) optionally transferring the comminuted PVD layer(s) into a dispersion or paste.