Color effect pigments and method of forming the same
A metallic effect pigment including a metallic, corrosion resistant reflective core of reflectivity from 40% to 80%; having deposited thereupon at least one dielectric coating layer formed of at least one metal oxide, the metal oxide layer having been formed by deposition on the core by hydrolysis of a hydrolyzable metal salt in an strongly acidic aqueous medium, and thereafter full transformation into the oxide by calcination.
1. An effect pigment comprising:
(a) a core formed of a metallic material of reflectivity from 40% to 80% selected from the group consisting of titanium, tantalum, zirconium, stainless steel and hastelloy;
(b) a non-interferent layer comprising tin dioxide which is arranged between layers (a) and (c); and
(c) at least one dielectric layer consisting of one or more oxide of a metal selected from iron, titanium and zirconium.
2. The pigment of claim 1 , wherein the metal oxide of dielectric layer (c) is a coloured oxide or coloured mixed oxide of iron and has a physical thickness of 100 to 400 nm and an index of refraction of 2.0 to 3.2.
3. The pigment of claim 2 , wherein said thickness is 250 to 400 nm.
4. The pigment of claim 2 , wherein said metal oxide is ferric oxide.
5. The pigment of claim 1 , wherein the metal oxide of dielectric layer (c) is a substantially colourless oxide of titanium or zirconium and has a physical thickness of 100 to 400 nm and an index of refraction of 2.0 to 2.7.
6. The pigment of claim 5 , wherein said thickness is 250 to 400 nm.
7. The pigment of claim 5 , wherein said metal oxide is titanium dioxide.
8. The pigment of claim 1 , wherein the metal oxide of layer (b) has a thickness of from 0.1 nm to 20 nm.
9. The pigment of claim 1 , further comprising a colour absorbing layer (d) further from said core than said dielectric layer, wherein the colour absorbing layer comprises at least one compound selected from the group consisting of Fe 2 O 3 , CoO, CoTiO 3 , Cr 2 O 3 , Fe 2 TiO 5 or SiO x , wherein x is less than one, and has a thickness of 5 to 50 nm.
10. The pigment of claim 1 , wherein said core is titanium.
11. The pigment of claim 2 , wherein said core is titanium.
12. The pigment of claim 5 , wherein said core is titanium.
13. The pigment of claim 8 , wherein said core is titanium.
14. The pigment of claim 9 , wherein said core is titanium.
15. The pigment of claim 10 , wherein said core (a) is superficially oxidized to a depth of from 0.1 nm to 20 nm.
16. The pigment of claim 1 , wherein said effect is a goniochromatic effect.
17. A composition comprising a high molecular weight organic material and a coloristically effective amount of an effect pigment according to claim 1 .
18. A composition of claim 17 , which is an automotive coating.
19. A process for pigmenting a high molecular weight organic material, wherein an effect pigment according to claim 1 is incorporated into said material.