RADAR TRANSPARENT, OPTICALLY REFLECTIVE SEMICONDUCTOR EFFECT PIGMENTS

Abstract

This invention deal with a flaky effect pigment comprising as optical active layer a single platelet consisting of a semiconductor material with a band gap in a range of 0.1 to 2.5 eV and having an average atomic composition of: a) Si.sub.(1-x)Ge.sub.x, wherein 0<x<1.00 or b) Si.sub.(1-y)Sn.sub.y, wherein 0<y<0.90 or c) Ge.sub.(1-z)Sn.sub.2, wherein 0<z0.60 or d) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0<m<1.00, 0<n<1.00 with the provisos that x<1.00; y<1.00, z<1.00 and m+n<1.00. These effect pigments exhibit attractive optical properties and are radartransparent.

Claims

1. A flaky effect pigment comprising as the only optical active layer a single platelet consisting of a semiconductor material with a band gap in a range of 0.1 to 2.5 eV, wherein the average thickness t.sub.a of the single semiconductor platelet is in a range of 5 to 160 nm and having an average atomic composition of: a) Si.sub.(1-x)Ge.sub.x, wherein 0<x<1.00 or b) Si.sub.(1-y)Sn.sub.y, wherein 0<y<0.90 or c) Ge.sub.(1-z)Sn.sub.z, wherein 0<z0.60 or d) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0<m<1.00, 0<n<1.00 with the provisos that x<1.00; y<1.00, z<1.00 and m+n<1.00.

2. The flaky effect pigment according to claim 1, wherein the band gap is in a range of 0.2 to 1.4 eV.

3. The flaky effect pigment according to claim 1, wherein the single platelet semiconductor has an average atomic composition of: a) Si.sub.(1-x)Ge.sub.x, wherein 0.01<x<0.9 or b) Si.sub.(1-y)Sn.sub.y, wherein 0.02y0.75 or c) Ge.sub.(1-z)Sn.sub.z, wherein 0.02z0.5 or d) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0.02m0.8, 0.02n0.75

4. The flaky effect pigment according to claim 1, wherein the single platelet semiconductor has an average atomic composition of: a) Si.sub.(1-x)Ge.sub.x, wherein 0.05x0.65 or b) Si.sub.(1-y)Sn.sub.y, wherein 0.05y0.55 or c) Ge.sub.(1-z)Sn.sub.z, wherein 0.05z0.4 or d) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0.05m0.65, 0.05n0.55.

5. The flaky effect pigment according to claim 1, wherein the effect pigment has a silvery appearance with an average thickness t.sub.a of the single semiconductor platelet in a range of 15 to 40 nm.

6. The flaky effect pigment according to claim 1, wherein the effect pigment has a colored appearance with an average thickness t.sub.a of the single semiconductor platelet in a range of larger than 40 to 160 nm.

7. The flaky effect pigment according to claim 1, wherein the d.sub.50 of the particle size distribution is in a range of 2 to 100 m.

8. The flaky effect pigment according to claim 1, wherein the aspect ratio d.sub.50/t.sub.a is in a range of 30 to 2000.

9. The flaky effect pigment according to claim 1, wherein the single semiconductor platelet is coated or encapsulated with a transparent not optically active metal oxide of refractive index n<1.8.

10. The flaky effect pigment according to claim 1, wherein the effect pigment is further coated with a surface modifier comprising one or more of an organofunctional silane, a titanate, an aluminate, a zirconate, a phosphate ester, a phosphonate ester, and a phosphite ester.

11. A method of manufacturing a flaky effect pigment comprising the steps of: a) providing a flexible substrate coated with a release agent, b) evaporating under ultra high vacuum conditions a semiconductor material with a band gap in a range of 0.1 to 2.5 eV onto the flexible substrate a), c) stripping the semiconductor film from the flexible substrate in a suitable solvent and comminuting the particles in the dispersion to obtain semiconductor flakes, and d) separating the semiconductor flakes from the solvent; the resulting flaky effect pigment comprising as the only optical active layer a single platelet consisting of a semiconductor material with a band gap in a range of 0.1 to 2.5 eV, wherein the average thickness t.sub.a of the single semiconductor platelet is in a range of 5 to 160 nm and having an average atomic composition of: a) Si.sub.(1-x)Ge.sub.x, wherein 0<x<1.00 or b) Si.sub.(1-y)Sn.sub.y, wherein 0<y<0.90 or c) Ge.sub.(1-z)Sn.sub.z, wherein 0<z0.60 or d) Si.sub.(1-m-n)Ge.sub.mSn.sub.n, wherein 0<m<1.00, 0<n<1.00 with the provisos that x<1.00; y<1.00, z<1.00 and m+n<1.00.

12. The method according to claim 11, wherein step b) is done by a roll-to-roll process.

13. The method according to claim 11, wherein step b) is done with an electron beam process.

14. A coating formulation comprising a binder and the flaky effect pigment according to claim 1.

15. (canceled)

16. The flaky effect pigment according to claim 3, wherein the single platelet semiconductor has an average atomic composition of a) Si.sub.(1-x)Ge.sub.x, wherein 0.02x0.8.

17. The flaky effect pigment according to claim 9, said metal oxide comprising SiO.sub.2.

18. The method according to claim 11, further comprising further size classifying the semiconductor flakes.

19. The method according to claim 11, further comprising dispersing the semiconductor flakes in a different solvent.

20. The flaky effect pigment according to claim 1, wherein the single platelet semiconductor has an average atomic composition of Si.sub.(1-x)Ge.sub.x, wherein 0<x<1.00.

21. The flaky effect pigment according to claim 1, wherein the single platelet semiconductor has an average atomic composition of Si.sub.(1-y)Sn.sub.y, wherein 0<y<0.90.

Description

EXAMPLES

Comparative Example 1

[0113] Commercially available Metalure Liquid Black (Eckart GmbH) which is a black PVD metal effect pigment with strong flop properties.

Comparative Example 2

[0114] Commercially available Metalure L-55700 (Eckart GmbH) which is a standard PVD aluminum effect pigment.

Example 1: Silicon-Germanium Composite

[0115] A silicon and germanium blend was deposited on a 30 cm wide clear polyester film coated with a releasing agent using ebeam PVD evaporation. The ebeam source was positioned 36 cm below the web during process and conditions were modified to achieve a silver coloration for the final pigment. The ebeam source accelerating voltage was held at a constant 10 kV throughout the run.

[0116] The materials obtained in Example 1 were all stripped from the polyester film and homogenized to a particles size of 19 m (D.sub.50 value). Pigments were prepared with a 10 wt. % non-volatile content (NVM) in propyl glycol methyl ether acetate. The average particle thickness t.sub.a, obtained via SEM analysis, is 23+/3 nm. The elemental silicon: germanium atomic ratio determined from energy dispersive spectroscopy is 45:55.

[0117] Pigment samples were adjusted to 5% NVM with propyl glycol methyl ether acetate for spray application in Deltron DBC500 Color Blender. Spray inks were formulated to target pigment volume concentrations between approximately 1.8 to 2.4%. Samples were applied in duplicate, achieving full coverage within 1-2 coats over polyester film and ABS plastic substrates. Panels were dried at ambient temperature for approximately 30 minutes between coats.

[0118] Gloss data were collected using a BYK Micro Tri-gloss meter. Additional optical data were collected using a BYK Mac meter. Optical data were collected on the polyester films on both the frontside (coating side) and backside of the film. The flop was calculated according to the common formula:

[00003]$\mathrm{Flop}\mathrm{index}=2.69{\left(L_{15}^{}-L_{110}^{}\right)}^{1.11}/{L_{45}^{*}}^{0.86}$

[0119] The results of these measurements are summarised in Tables 1a to d below.

Tables 1a to d: Optical Data Collected from Silicon Germanium Alloy Effect Pigments of Example 1 at Different Binder: Pigment Ratios and Different Substrates.

TABLE-US-00001 TABLE 1a Wt.-ratio Panel Panel Binder:Pigment Side Type L*.sub.15 L*.sub.15 L*.sub.25 L*.sub.45 L*.sub.75 L*.sub.110 12:1 Front Polyester 134.9 116.6 72.6 30.1 11.7 6.2 12:1 Back Polyester 128.2 113.1 72.2 31.2 12.5 6.5 12:1 Front ABS 134.2 117.0 73.4 31.8 12.5 6.7 16:1 Front Polyester 131.0 114.9 73.9 32.9 13.3 6.9 16:1 Back Polyester 125.8 110.8 72.4 33.0 13.9 7.4 16:1 Front ABS 132.6 116.4 74.9 33.4 13.3 6.7

TABLE-US-00002 TABLE 1b Wt.-ratio Panel Panel Binder:Pigment Side Type a*.sub.15 a*.sub.15 a*.sub.25 a*.sub.45 a*.sub.75 a*.sub.15 12:1 Front Polyester 0.1 0.1 1.0 1.3 1.0 0.1 12:1 Back Polyester 0.8 0.4 0.8 1.4 1.0 0.8 12:1 Front ABS 0.5 0.2 0.8 1.2 1.0 0.5 16:1 Front Polyester 0.1 0.1 0.9 1.2 1.0 0.1 16:1 Back Polyester 0.9 0.4 0.7 1.3 1.0 0.9

TABLE-US-00003 TABLE 1c Wt.-ratio Panel Panel Binder:Pigment Side Type b*.sub.15 b*.sub.15 b*.sub.25 b*.sub.45 b*.sub.75 b*.sub.110 12:1 Front Polyester 0.3 1.0 2.3 2.8 2.1 1.3 12:1 Back Polyester 1.9 2.7 3.3 3.1 1.6 0.3 12:1 Front ABS 0.8 0.0 1.9 2.6 2.2 1.5 16:1 Front Polyester 0.2 1.0 2.2 2.7 2.2 1.6 16:1 Back Polyester 1.4 2.1 2.9 2.8 1.4 0.3

TABLE-US-00004 TABLE 1d Wt.-ratio Binder:Pigment Panel Side Panel Type Gloss20 Gloss60 Flop 12:1 Front Polyester 22 69 26.6 12:1 Back Polyester 106 140 24.9 12:1 Front ABS 18 61 25.4 16:1 Front Polyester 20 64 24.1 16:1 Back Polyester 141 139 22.9

Example 2: Silicon-Germanium Pigment to Binder Ratio Modification

[0120] A silicon and germanium blend was deposited on a 30 cm wide clear polyester film coated with a releasing agent using ebeam PVD evaporation. The ebeam source was positioned 36 cm below the web during process and conditions were modified to achieve a silver coloration for the final pigment. The ebeam source accelerating voltage was held at a constant 10 kV throughout the run.

[0121] The materials obtained in Example 2 were all stripped from the polyester film and homogenized to a particles size of 14 m (d.sub.50 value). Pigments were prepared with a 10 wt. % non-volatile content (NVM) in propyl glycol methyl ether acetate. The average particle thickness t.sub.a, obtained via SEM analysis, is 29+/3 nm. The elemental silicon: germanium atomic ratio determined from energy dispersive spectroscopy is 47:53.

[0122] A spray application ladder was designed and executed. Multiple spray inks were formulated to pigment volume concentrations calculated between 3-61%, using Deltron DBC500 Color Blender. Metals content was held constant throughout all ink formulations. Samples were applied in duplicate over ABS panel substrate. The entirety of each ink was applied in a single coat to maintain consistent metals distribution throughout all panels. Select panels from each set were clear-coated with Deltron DC4000 and force-dried for an additional 60 minutes at 60 C. Panels were dried at ambient temperature for approximately 30 minutes between coats.

[0123] Gloss data were collected using a BYK Micro Tri-gloss meter. Additional optical data were collected using a BYK Mac colorimeter. The results of these measurements are summarised in Table 2 below.

Tables 2a,b and c: Gloss-, Flop-, L*-, a*- and b* Values for Example 3 at Different Binder: Pigment Ratios

TABLE-US-00005 Wt.-ratio Clear Gloss Gloss Binder:Pigment Coat 20 60 Flop L*.sub.15 L*.sub.15 L*.sub.25 L*.sub.45 L*.sub.75 L*.sub.110 5:1 No 39 94 33.1 129 110 61.5 22.2 7.3 3.9 5:1 Yes 99 107 21.9 126 113 75.7 35.4 14.3 7.6 7:1 No 43 96 31.2 132 113 65.1 24.6 8.3 4.1 7:1 Yes 99 108 24 129 116 76.3 33.9 12.5 6.0 9:1 No 30 81 30.4 137 118 69.6 26.8 9.3 4.5 9:1 Yes 97 106 23.8 131 118 79 35.1 12.8 5.9 12:1 No 23 68 26.7 136 119 74.2 31.2 11.8 5.7 12:1 Yes 96 104 20.1 124 113 79.4 39.1 16.1 8.29 15:1 No 20 64 24.1 134 119 78.2 34.7 13.7 6.64 15:1 Yes 93 102 18.8 121 111 80.6 41.1 17.7 9.08

TABLE-US-00006 TABLE 2b Wt.-ratio Clear Binder:Pigment Coat a.sub.15 a.sub.15 a.sub.25 a.sub.45 a.sub.75 a.sub.110 5:1 No 0.35 0.1 1.45 1.56 1.11 0.42 5:1 Yes 1.78 1.2 0.12 0.4 0.52 0.31 7:1 No 0.42 0.08 1.47 1.61 1.2 0.5 7:1 Yes 1.33 0.77 0.35 0.84 0.86 0.5 9:1 No 0.65 0.12 1.35 1.7 1.3 0.65 9:1 Yes 0.78 0.29 0.58 1.06 1.07 0.67 12:1 No 0.68 0.21 1.12 1.63 1.42 0.83 12:1 Yes 0.73 0.22 0.56 0.99 1.05 0.84 15:1 No 0.28 0.09 1.03 1.5 1.35 1.02 15:1 Yes 0.15 0.2 0.75 1.12 1.19 1.02

TABLE-US-00007 TABLE 2c Wt.-ratio Clear Binder:Pigment Coat b.sub.15 b.sub.15 b.sub.25 b.sub.45 b.sub.75 b.sub.110 5:1 No 2.48 0.62 2.59 3.17 1.83 0.85 5:1 Yes 0.47 0.55 1.61 1.71 1.61 1.19 7:1 No 1.21 0.45 3.15 3.4 2.31 1.03 7:1 Yes 0.5 1.43 2.42 2.5 2.22 1.41 9:1 No 0.32 1.05 3.25 3.66 2.67 1.24 9:1 Yes 2.43 2.77 3.06 2.86 2.56 1.64 12:1 No 0.21 1.23 3.05 3.51 2.76 1.7 12:1 Yes 2.59 2.89 3.11 2.85 2.52 2.16 15:1 No 1.54 2.11 3.01 3.29 2.79 1.96 15:1 Yes 3.32 3.29 3.29 2.95 2.64 2.36

[0124] The effect pigment of this example exhibits rather neutral color tones with high flop values making it look as attractive effect pigment with metallic look.

[0125] When increasing the binder/pigment ratio flop and gloss values tend to be reduced as here with reduced binder concentration, there is less spacing between the flakes as the system dries. This ensures that the pigments orient better in a flat/parallel positions relative to the substrate to produce high reflectivity.

Example Series 3: SiSn

[0126] Further samples of silicon alloy flakes were manufactured according to Example 2, but with tin instead of germanium as the alloy material. Three experiments were conducted under different conditions in order to vary the composition and thickness of the resulting alloy flakes. The Si:Sn composition and flake thickness were varied and verified with SEM analysis, as shown in Table 4. In this analysis oxygen contents were excluded.

TABLE-US-00008 TABLE 3 Thickness and composition excluding oxygen Si:Sn Atomic Average Sample Ratio Thickness (nm) Example 3a 79:21 29 Example 3b 69:31 26 Example 3c 70:30 35

[0127] Multiple spray inks were formulated with binder: pigment ratios shown in Table 4, using Deltron DBC500 Color Blender. Metals content was held constant throughout all ink formulations. Samples were applied in duplicate over ABS panel substrate. The entirety of each ink was applied in a single coat to maintain consistent metals distribution throughout all panels. Select panels from each set were clear-coated with Deltron DC4000 and force-dried for an additional 60 minutes at 60 C. Panels were dried at ambient temperature for approximately 30 minutes between coats.

[0128] Gloss data were collected using a BYK Micro Tri-gloss meter. Additional optical data were collected using a BYK Mac colorimeter. The results of these measurements are summarised in Table 4 below. Data of the Comparative Examples 1 (Commercially available Metalure Liquid Black) and 2 (Commercially available Metalure L-55700) are shown for comparison.

Tables 4a to c: Optical Data from Silicon Tin Alloy Effect Pigments of Example 3

TABLE-US-00009 TABLE 4a Binder:Pigment Clear Gloss Gloss Sample ratios Coat 20 60 Flop L*.sub.15 L*.sub.15 L*.sub.25 L*.sub.45 L*.sub.75 L*.sub.110 Ex. 3a 7:1 No 3 13 16.5 133.3 110.5 83.4 45.1 20.5 12.3 Ex. 3a 7:1 Yes 96 98 8.29 75.0 72.5 63.3 44.8 28.7 20.0 Ex. 3b 7:1 No 3 16 17.25 133.0 110.0 81.2 43.2 19.4 11.2 Ex. 3b 7:1 Yes 95 98 9.08 77.9 74.6 64.0 44.0 27.2 18.5 Ex. 3c 3.5:1.sup. No 14 56 27.72 157.5 134.2 82.1 33.8 14.2 9.1 Ex. 3c 3.5:1.sup. Yes 99 105 17.21 128.4 117.0 85.7 45.7 22.3 14.1 Ex. 3c 7:1 No 13 50 23.65 148.8 129.0 83.4 38.0 16.8 10.2 Ex. 3c 7:1 Yes 98 102 13.14 113.1 105.3 83.0 50.1 27.8 18.7 Comp. 7:1 No 8 37 18.26 116.6 101.3 70.3 36.8 17.4 9.6 Ex. 1 Comp. 7:1 Yes 95 98 9.9 79.6 75.4 63.2 42.4 25.49 16.6 Ex. 1 Comp. 7:1 No 37 104 26.0 187.0 161.4 98.8 42.7 23.24 20.0 Ex. 2 Comp. 7:1 Yes 105 120 19.2 172.3 154.9 109.3 54.7 29.2 24.3 Ex. 2

TABLE-US-00010 TABLE 4b Binder:Pigment Clear Sample ratios Coat a*.sub.15 a*.sub.15 a*.sub.25 a*.sub.45 a*.sub.75 a*.sub.110 Ex. 3a 7:1 No 1.27 1.19 0.84 0.13 0.61 0.69 Ex. 3a 7:1 Yes 1.22 1.07 0.84 0.4 0.14 0.1 Ex. 3b 7:1 No 0.91 0.89 0.75 0.38 0.08 0.2 Ex. 3b 7:1 Yes 1.69 1.51 1.25 0.74 0.38 0.27 Ex. 3c 3.5:1.sup. No 0.57 0.21 0.13 0.36 0.4 0.34 Ex. 3c 3.5:1.sup. Yes 0.34 0.06 0.08 0.21 0.25 0.24 Ex. 3c 7:1 No 0.32 0.46 0.62 0.57 0.53 0.46 Ex. 3c 7:1 Yes 0.5 0.61 0.54 0.41 0.37 0.35 Comp. 7:1 No 1.28 1.2 0.88 0.54 0.32 0.28 Ex. 1 Comp. 7:1 Yes 1.34 1.19 1.06 0.78 0.59 0.51 Ex. 1 Comp. 7:1 No 1.00 0.58 0.02 0.2 0.13 0.04 Ex. 2 Comp. 7:1 Yes 1.37 0.92 0.6 0.29 0.21 0.49 Ex. 2

TABLE-US-00011 TABLE 4c Binder:Pigment Clear Sample ratios Coat b*.sub.15 b*.sub.15 b*.sub.25 b*.sub.45 b*.sub.75 b*.sub.110 Ex. 3a 7:1 No 0.78 0.42 0.11 0.71 1.93 2.05 Ex. 3a 7:1 Yes 0.23 0.40 0.67 0.94 1.23 1.19 Ex. 3b 7:1 No 0.38 0.31 0.4 0.08 0.61 0.74 Ex. 3b 7:1 Yes 1.02 0.86 0.66 0.29 0.23 0.32 Ex. 3c 3.5:1.sup. No 3.85 4.73 3.52 2.36 1.64 1.45 Ex. 3c 3.5:1.sup. Yes 5.55 5.27 4.02 2.46 1.73 1.57 Ex. 3c 7:1 No 4.48 4.71 3.78 2.51 1.82 1.73 Ex. 3c 7:1 Yes 6.22 5.77 4.62 2.94 2.13 1.99 Comp. 7:1 No 0.96 0.76 0.32 0.12 0.09 0.2 Ex. 1 Comp. 7:1 Yes 0.26 0.19 0.18 0.05 0.03 0.03 Ex. 1 Comp. 7:1 No 2.09 1.41 0.25 1 0.44 0.58 Ex. 2 Comp. 7:1 Yes 0.68 0.5 0.63 0.14 0.17 0.1 Ex. 2

[0129] From Table 4a it can be well seen that the inventive examples have a flop in between Comparative Example 1 (Metalure Liquid Black) and Comparative Example 2 (standard PVD aluminum pigment). The a*-, b*-values are small and show an essentially neutral color tone. Visually the effect pigments appear as silvery color tones with strong lightness flop.

Examples 4a,b: SiGe and SiSn Extended Testing

[0130] Samples of an silicon germanium and silicon tin alloy flakes were manufactured according to parameters outlined in Examples 1-3, but with slightly different compositions. The materials obtained in Example 4 were stripped from their polyester films and homogenized to particle sizes of 12-15 m (d.sub.50 value). Pigment dispersions were prepared with a 10 wt. % non-volatile content (NVM) in propyl glycol methyl ether. The SEM/EDX analysis revealed alloy compositions of Si.sub.46Ge.sub.54 and Si.sub.66Sn.sub.34, respectively. The average particle thickness (t.sub.a) for the SiGe and SiSn alloys were found to be 28+/3 nm and 29+/3 nm, respectively. In this analysis oxygen contents were excluded.

[0131] A binder formulation was made by mixing and stirring 43.5 parts of NC E 1160 (from Hagederon AG, Germany) binder in isopropyl 30, with 9 wt.-% binder content in butyl acetate 85 together with 26.5 parts butyl acetate, 26.5 part xylol, 0.6 parts butyl diglycol, 1.6 parts butyl glycol to which 0.3 parts of Byk 358 N and 1.0 part of Byk 120 were added as additives.

[0132] Multiple spray inks were formulated with binder: pigment ratios shown in Table 5. Viscosity was adjusted using a 1:1 solvent mixture of butyl acetate and xylol. Spray inks were applied to ABS panels using a spray-coating apparatus APL 3.3 from Company Oerter, Germany. Each formulation was sprayed four times to achieve full-tone coverage of each effect pigment.

[0133] The radar transparency measurements were done with microwave radiation with a frequency of 76.5 GHz using as a measurement system an RMS-D-77/79G apparatus from Perisens GmbH, Germany. Additional optical data were collected using a BYK Mac colorimeter.

[0134] Radar attenuation and optical results of the sprayed panels are shown in Table 5. Radar data has been background corrected to account for loss produced by the uncoated substrate.

Tables 5a,b,c: Radar and Optical Characterization of Example 3 Against Comp. Examples

TABLE-US-00012 TABLE 5a Attenuation/ Radar Loss (dB), Wt.-ratio Background Sample Binder:Pigment corrected Flop L*.sub.15 L*.sub.15 L*.sub.25 L*.sub.45 L*.sub.75 L*.sub.110 Example 4a 3.8:1 ~0 30.1 110.1 89.3 48.3 18.7 7.7 4.2 (SiGe) Example 4b 4.2:1 0.07 42.1 132.15 113.58 72.88 34.54 16.45 9.96 (SiSn) Comp. 4.5:1 1.55 37.0 101.9 82.4 42.2 13.6 4.30 2.30 Example 1 Comp. 4.5:1 2.15 24.8 155.5 129.3 74.0 33.4 20.5 17.2 Example 2

TABLE-US-00013 TABLE 5b Wt. % ratio Sample Binder:Pigment a*.sub.15 a*.sub.15 a*.sub.25 a*.sub.45 a*.sub.75 a*.sub.110 Example 4a 3.8:1 2.77 2.57 2.33 1.31 0.96 0.46 (SiGe) Example 4b 4.2:1 1.20 1.19 0.48 0.15 0.04 0.05 (SiSn) Comp. 4.5:1 0.74 0.09 0.05 0.06 0.05 0.74 Example 1 Comp. 4.5:1 0.47 0.33 0.44 0.41 0.31 0.47 Example 2

TABLE-US-00014 TABLE 5c Wt. % ratio Sample Binder:Pigment b*.sub.15 b*.sub.15 b*.sub.25 b*.sub.45 b*.sub.75 b*.sub.110 Example 4a 3.8:1 2.77 2.57 2.33 1.31 0.96 0.84 (SiGe) Example 4b 4.2:1 6.59 6.58 4.89 2.73 1.67 0.29 (SiSn) Comp. 4.5:1 1.98 1.39 0.64 0.27 0.20 0.12 Example 1 Comp. 4.5:1 1.25 1.2 1.33 0.82 0.29 1.55 Example 2

[0135] It can be well seen that the silicon germanium and silicon tin alloy effect pigments produce a radar attenuation of essentially zero, while both metal effect pigments display significant losses. All applications were realized with full hiding power of the effect pigments.

[0136] When compared in full-tone hiding, the optical flop exhibited by the effect pigment alloys of Example 4 is comparable to that of the effect pigments of Comparative Examples 1 and 2. The L*15 value, typically considered a brightness indicator, is between Comparative Example 1 and 2.

[0137] Examples 5: SiGe, and SiSn and Comparative Examples 3: Si Further samples of silicon-germanium and silicon-tin alloy flakes were manufactured according to Examples 1-3. Additional comparative Si-only samples were manufactured with varying silicon thicknesses. The Si:Ge, Si:Sn, and Si composition and average particle thickness (t.sub.a) were verified with SEM analysis, as shown in Table 6. Oxygen contents were excluded in this analysis.

[0138] The deposited materials were all stripped from the polyester film and homogenized to a particles size of 12-15 m (d.sub.50 value). Inks were prepared in an Eckart's in-house binder system, composed of Hagedorn H7 Nitrocellulose binder (obtainable from Hagedorn AG, Osnabrck, Germany) in a solvent blend of ethyl acetate and propylene glycol methoxy ether. Formulations were based on a 1.85:1 weight ratio of binder to metal content with a 1.5% total metal content. The samples were drawn down on a flat polyester film with a wire wound rod to a 40 m wetfilm thickness.

[0139] Gloss and color data were collected from the reverse side of each polyester film using a BYK Micro Tri-gloss meter and BYK Mac colorimeter, respectively. Opacity data were collected using an X-rite 341C transmission densitometer by averaging 6 collection points along the coated polyester film. The results of these measurements are summarised in Table 6. Data of the Comparative examples 1 (Commercially available Metalure Liquid Black) and 2 (Commercially available Metalure L-55700) are shown for comparison.

Tables 6a,b: Optical, Thickness, and Compositional Data from Effect Pigments of Example 5 and Comparative Examples.

TABLE-US-00015 ta Si Ge/Sn Opacity Sample (nm) at % at % (OD) G20 G60 Ex. 5a 27 43 57 1.58 280 209 (SiGe) Ex. 5b 29 67 34 1.56 258 200 (SiSn) Comp. 27 100 0 0.47 206 172 Ex. 3a (Si) Comp. 29 100 0 0.53 195 170 Ex. 3b (Si) Comp. 31 100 0 0.57 207 182 Ex. 3c (Si) Comp. N/A 1.39 201 177 Ex. 1 Comp. N/A 2.96 430 334 Ex. 2

TABLE-US-00016 TABLE 6b Sample C*.sub.15 C*.sub.15 C*.sub.25 C*.sub.45 C*.sub.75 C*.sub.110 Ex. 5a 3.10 4.63 3.53 1.76 1.24 1.34 (SiGe) Ex. 5b 2.40 1.24 1.36 2.42 0.49 1.00 (SiSn) Comp. 28.56 27.05 18.5 9.5 6.31 4.78 Ex. 3a (Si) Comp. 23.23 23.91 17.8 9.46 6.31 4.93 Ex. 3b (Si) Comp. 24.23 23.12 14.81 6.99 4.31 2.98 Ex. 3c (Si) Comp. 2.29 1.48 0.63 0.14 0.59 0.88 Ex. 1 Comp. 2.17 1.07 0.69 0.61 0.42 1.29 Ex. 2

[0140] From Tables 6, it can be well seen that the inventive examples display far more neutral color tones as compared to silicon-only samples (Comparative Examples 3) of comparative thickness. Moreover, the SiSn inventive example 5b is nearly as color neutral as the Comparative Example 2 aluminum sample. The gloss values of the inventive examples are also superior to both the silicon-only samples and Comparative Example 1. The opacity values of the inventive examples are also superior to both the silicon-only samples and Comparative Example 1. Thus, color neutrality, gloss, and coverage of the inventive silicon-germanium and silicon-tin alloys are shown to be superior to the silicon-only samples.