Effect pigments having a reflective core and semiconductor layers

Abstract

Disclosed herein is an effect pigment having a layer stack which comprises a highly reflective metallic flake having a first major interface and opposed to this first interface a second major interface, and at least one side surface and directly adjacent on one or of both of these major interfaces a layer of a semiconducting material having an average atomic composition of: a) Si.sub.(1-x)Sn.sub.x, wherein 0<x<0.90 or b) Ge.sub.(1-y)Sn.sub.y, wherein 0<y0.80 or c) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0<m<1.00, 0<n<1.00 and with the proviso that m+n<1.00.

Claims

1. An effect pigment having a layer stack which comprises a highly reflective metallic flake having a first major interface and opposed to this first interface a second major interface, and at least one side surface and directly adjacent on one or of both of these major interfaces a layer of a semiconducting material having an average atomic composition of: a) Si.sub.(1-x)Sn.sub.x, wherein 0<x<0.90 or b) Ge.sub.(1-y)Sn.sub.y, wherein 0<y0.80 or c) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0<m<1.00, 0<n<1.00 and with the proviso that m+n<1.00.

2. An effect pigment according to claim 1, wherein the highly reflective metallic flake is coated on both major interfaces with the semiconductor material and wherein additionally the semiconductor layers are coated with further dielectric, reflective or absorbing materials.

3. An effect pigment according to claim 1, wherein the layer stack consists of the highly reflective metallic flake having a first major interface and opposed to this first interface a second major interface, and at least one side surface and directly adjacent on both of these major interfaces a layer of a semiconducting material having an average atomic composition of: a) Si.sub.(1-x)Sn.sub.x, wherein 0<x<0.90 or b) Ge.sub.(1-y)Sn.sub.y, wherein 0<y0.80 or c) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0<m<1.00, 0<n<1.00 and with the proviso that m+n<1.00.

4. The effect pigment of claim 1, wherein the semiconducting layer or layers have a bandgap in a range of 0.1 to 2.5 eV.

5. The effect pigment of claim 1, wherein the highly reflective metal flake is selected from the group consisting of aluminum, copper, chromium, titanium, zinc, silver, gold or alloys thereof.

6. The effect pigment according to claim 1, wherein the average atomic composition of the semiconducting material is: a) Si.sub.(1-x)Sn.sub.x, wherein 0.02x0.75 or b) Ge.sub.(1-y)Sn.sub.y, wherein 0.02y0.60 or c) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0.02m0.8 and 0.02n0.75.

7. A flaky effect pigment according to claim 1, wherein the average atomic composition of the semiconducting material is: a) Si.sub.(1-x)Sn.sub.x, wherein 0.05x0.55 or b) Ge.sub.(1-y)Sn.sub.y, wherein 0.05y0.50 or c) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0.05m0.65 and 0.05n0.55.

8. The effect pigment according to claim 1, wherein the highly reflective metallic flake has an average thickness in the range from 5 to 500 nm.

9. The effect pigment according to claim 1, wherein the layer of the semiconductor material has a mean thickness in the range from 5 to 200 nm.

10. The effect pigment according to claim 1, wherein the effect pigment is further encapsulated with an outer layer.

11. The effect pigment according to claim 10, wherein the further encapsulating layer consists of a layer of Mo-oxide, SiO.sub.2, AI.sub.2O.sub.3 or a surface modifier.

12. The effect pigment according to claim 11, wherein the further encapsulating layer consists of a surface modifier, the surface modifier comprising one or more of an organofunctional silane, a phosphate ester, a phosphonate esters, and a phosphite esters.

13. An ink composition comprising the effect pigment of claim 1 and a binder.

14. A product comprising the effect pigment of claim 1 in the form of a cosmetic composition.

15. A composition comprising a plastic and the effect pigment of claim 1.

16. A method of manufacturing an effect pigment using a PVD process comprising: a) coating a thin, flexible substrate with a release coat agent, b) depositing a first semiconductor layer onto the flexible substrate using a roll-to-roll process, c) depositing a layer of a highly reflective metal onto the first semiconductor layer, d) depositing a second semiconductor layer onto the highly reflective metal layer, and e) stripping the material stack from the flexible substrate in a solvent; the resulting effect pigment having a layer stack which comprises a highly reflective metallic flake having a first major interface and opposed to this first interface a second major interface, and at least one side surface and directly adjacent on one or of both of these major interfaces a layer of a semiconducting material having an average atomic composition of: a) Si.sub.(1-x)Sn.sub.x, wherein 0<x<0.90 or b) Ge.sub.(1-y)Sn.sub.y, wherein 0<y0.80 or c) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0<m<1.00, 0<n<1.00 and with the proviso that m+n<1.00.

17. The method of manufacturing according to claim 16, wherein the highly reflective metal has a thickness in a range of 5 to 500 nm.

18. The method of manufacturing according to claim 16, wherein the first semiconductor layer and the second semiconductor layer are composed of the same material.

19. The method of claim 16, further comprising one or more steps of particle sizing, particle classification and solvent dispersion.

Description

EXAMPLES

Example 1a, and 1b

(1) 3-Layer Material (SiSnAlSiSn,)

(2) A layer of SiSn alloy (solid solution, Sn a solute) was deposited on a 30 cm wide clear polyester film coated with a CAB (Cellulose Acetate Butyrate) based release agent using e-beam PVD evaporation. A second discrete layer of Al was deposited onto the SiSn alloy using same system with targeted optical density of approximately 1.0-1.5 OD. 3-layer materials were prepared after the deposition of third discrete layer of Si and Sn alloy, where optical densities of each layer are approximately 0.5-0.7 OD for 1a, and 0.4-0.6 OD for 1b, onto the Al layer in the similar condition of the first layer. In each process, the e-beam source was positioned 36 cm below the film. The e-beam source accelerating voltage was held at a constant 10 kV throughout the run.

(3) In the alloy deposition steps, the first SiSn alloy-layer was deposited on the CAB side of a clear polyester film (web) using PVD e-beam evaporation. In-situ optical transmission sensors were utilized to determine the alloy thickness, and e-beam current and web-speed was manipulated to target the appropriate layer thickness. The third layers was performed in the similar condition after the Al deposition.

(4) The thickness of the two SiSn layers was targeted to be the same, so that the web-side and metal side of each condition would be the same color. Silver-green (Ex. 1a) and blue (Ex. 1b) color tones were each targeted and successfully produced. The coloration of the web and metal side of the films matched well in each material set. The coloration of the web and metal side of the films matched well in each material set.

(5) In the second step, an Al layer was deposited corresponding to approximately targeted optical density. Optical transmission sensors in combination with current adjustment was utilized to target appropriate Al thickness.

(6) The average SiSn and Al layer thickness for Example 1a, obtained via SEM analysis, is 57+/3 nm and 18+/3 nm with a silicon: tin atomic ratio determined from energy dispersive spectroscopy of 82:18. The average SiSn and Al layer thickness for Example 1b, obtained via SEM analysis, is 47+/3 nm and 18+/3 nm with a silicon: tin atomic ratio determined from energy dispersive X-ray spectroscopy of 82:18.

Example 2:3-Layer Material (GeSnAlGeSn,)

(7) As the process was described in example 1, A layer of GeSn alloy (solid solution, Sn a solute) was deposited on a 30 cm wide clear polyester film coated with a CAB (Cellulose Acetate Butyrate) based release agent using e-beam PVD evaporation for example 2. A second discrete layer of Al was deposited onto the GeSn alloy using same system with targeted optical density of approximately 1.0-1.5 OD. 3-layer materials were prepared after the deposition of third discrete layer of Ge and Sn alloy with optical density that is approximately 0.5-0.75 OD, onto the Al layer in the similar condition of the first layer. In each process, the e-beam source was positioned 36 cm below the film. The e-beam source accelerating voltage was held at a constant 10 kV throughout the run.

(8) In the alloy deposition steps, the first GeSn alloy-layer was deposited on the CAB side of a clear polyester film (web) using PVD e-beam evaporation. In-situ optical transmission sensors were utilized to determine the alloy thickness, and e-beam current and web-speed was manipulated to target the appropriate layer thickness. The third layers was performed in the similar condition after the Al deposition.

(9) The thickness of the two GeSn layers was targeted to be the same, so that the web-side and metal side of each condition would be the same color. A blue color tone was targeted and successfully produced. The coloration of the web and metal side of the films matched well in this material set.

(10) In the second step, an Al layer was deposited corresponding to approximately targeted optical density. Optical transmission sensors in combination with current adjustment was utilized to target appropriate Al thickness.

(11) The average GeSn and Al layer thickness for Example 2, obtained via SEM analysis, is 25+/3 nm and 20+/3 nm with a germanium: tin atomic ratio determined from energy dispersive X-ray spectroscopy of 80:20.

(12) The materials obtained in Example 1a, and 1b, and 2 were all stripped from the polyester film and milled/crushed to a particles size listed in Table 1 (D50 value). Pigments were prepared with a 25 wt. % in ethanol. Inks were prepared a binder system, composed of Hagedorn H7 Nitrocellulose binder (obtainable from Hagedorn AG, Osnabrck, Germany) in a solvent blend of ethyl acetate and propylene glycol monomethyl ether. Formulations were based on weight ratios of metals content to binder, with a binder-to-pigment weight ratio of 31:69. The samples were drawn down on a flat BYK drawdown card at a wet-film thickness of 40 m. Gloss data were collected using a BYK Micro Tri-gloss meter. Additional optical data were collected using a BYK Mac meter. The results of these measurements are summarised in Table 1.

(13) TABLE-US-00001 TABLE 1 Optical data of Examples Particle Size D50 Flop L*.sub.(15) Visual Sample (m) Index (trans) L*.sub.15 L*.sub.45 a*.sub.15 b*.sub.15 color Ex. 1a 15.7 41 131 110 18 4.5 4.9 Silvery green Ex. 1b 15.1 36 111 94 17 5 13 Teal blue Ex. 2 14.1 25 110 91 24 5.7 15 Teal blue