USE OF FLAKE-FORM EFFECT PIGMENTS FOR INCREASING THE INFRARED REFLECTION OF A DARK OR BLACK LAYER COMPOSITE

Abstract

The present invention relates to the use of flake-form effect pigments for increasing the infrared reflection of a dark or black layer composite, consisting of a substrate and a coating on the substrate, and to a dark or black layer composite of this type which has increased infrared reflection, in particular in the near infrared (NIR), compared with conventional dark or black layer composites which comprise only carbon-containing black pigments.

Claims

1. Use of flake-form effect pigments for increasing the infrared reflection of a dark or black layer composite consisting of a substrate and a coating on the substrate, where the coating, in addition or as an alternative to a carbon-containing black pigment, comprises at least one flake-form effect pigment which has at least one Fe.sub.3O.sub.4-containing layer or FeTiO.sub.3-containing layer on a flake-form Al.sub.2O.sub.3 or SiO.sub.2 support, where the layer composite has an L* 15 value in the range from 1 to 60, and where the infrared reflection of the layer composite is increased, at least in the wavelength range from 850 nm to 1570 nm, compared with a dark or black layer composite comprising a substrate and a coating where the layer composite comprises the carbon-containing black pigment, has an L*15 value in the said range and does not comprise at least one flake-form effect pigment.

2. Use according to claim 1, characterised in that the dark or black layer composite does not comprise a carbon-containing black pigment.

3. Use according to claim 1, characterised in that the carbon-containing black pigment is present in the substrate and in that the coating does not comprise the carbon-containing black pigment.

4. Use according to claim 1, characterised in that the carbon-containing black pigment and the at least one flake-form effect pigment are present together in a layer of the coating.

5. Use according to claim 1, characterised in that the carbon-containing black pigment and the at least one flake-form effect pigment are in each case present in two layers of the coating which are separated from one another.

6. Use according to one or more of claims 1 to 5, characterised in that at least two flake-form effect pigments which are different from one another and have flake-form supports which are different from one another are present in the coating.

7. Use according to one or more of claims 1 to 6, characterised in that the infrared reflection of the layer composite is increased specifically in the wavelength region 900±50 nm or in the region 1550±20 nm.

8. Use according to one or more of claims 1 to 7, characterised in that flake-form effect pigments which have a flake-form Al.sub.2O.sub.3 support are employed.

9. Use according to one or more of claims 1 to 8, characterised in that the substrate is a film, a plate or a moulding, in each case made from plastic, metal or a composite material, where the substrate may optionally have been pre-treated or pre-coated and the substrate and/or a pre-coating optionally comprises the carbon-containing black pigment.

10. Dark or black layer composite having increased infrared reflection, consisting of a substrate and a coating on the substrate, characterised in that the coating, in addition or as an alternative to a carbon-containing black pigment, comprises at least one flake-form effect pigment which has at least one Fe.sub.3O.sub.4-containing layer or FeTiO.sub.3-containing layer on a flake-form Al.sub.2O.sub.3 or SiO.sub.2 support, where the dark or black layer composite has an L*15 value in the range from 1 to 60 and where the infrared reflection of the layer composite is higher, at least in the wavelength range from 850 nm to 1570 nm, than the infrared reflection of a comparative layer composite which comprises the carbon-containing black pigment, has an L* 15 value in the said range and does not comprise at least one flake-form effect pigment.

11. Dark or black layer composite according to claim 10, characterised in that the infrared reflection, at least in the wavelength region 900±50 nm or in the wavelength region 1550±20 nm, is higher than the infrared reflection of the comparative coating.

12. Dark or black layer composite according to claim 10 or 11, characterised in that at least two flake-form effect pigments which are different from one another and which have flake-form supports which are different from one another are present in the coating.

13. Dark or black layer composite according to one or more of claims 10 to 12, characterised in that the coating does not comprise a carbon-containing black pigment.

14. Dark or black layer composite according to one or more of claims 10 to 13, characterised in that the coating comprises the carbon-containing black pigment and the at least one flake-form effect pigment in a single layer, which is optionally part of a multilayer system.

15. Dark or black layer composite according to one or more of claim 10 to 14, characterised in that the coating comprises the carbon-containing black pigment and the at least one flake-form effect pigment in each case in layers of a multilayer system which are separated from one another.

16. Dark or black layer composite according to one or more of claims 10 to 15, characterised in that the at least one flake-form effect pigment is present in a proportion of 1 to 60% by weight, based on weight of the layer, in the layer of the coating that comprises the at least one flake-form effect pigment.

17. Dark or black layer composite according to one or more of claims 10 to 16, characterised in that it is a motor vehicle part or a traffic control device.

18. Dark or black layer composite according to claim 17, characterised in that the motor vehicle part is an external bodywork part or component of a motor vehicle, and the motor vehicle has a driving assistance system or is autonomously controlled.

Description

EXAMPLES

[0076] Various samples of coatings are produced as follows:

[0077] Black- and white-coated test panels from Leneta (Leneta T12G Metopac, carbon-containing black pigment present in the black coating) are in each case coated over the entire area with a coating composition which, besides a commercially available binder and a solvent (varnish WBC000 from MIPA SE, Germany), comprises a pigment mass concentration PMC of 18% of dry weight of flake-form effect pigments in accordance with the invention. The coating is carried out by means of a pneumatic spray process with a dry-layer thickness in the range from 12 to 15 μm. After thermal curing of this colour layer, a colourless clear coat (MIPA CC4, MIPA SE) is applied to the colour layer (dry-layer thickness about 50 μm). The samples obtained in this way are measured using a BYK-mac i goniospectrophotometer (BYK Gardner GmbH, DE) in SMC 5 mode over the part of the surface of the test panel that has been pre-coated black. For comparative purposes, samples are produced by the same process, but with a different pigment mass concentration).

Example 1

[0078] Comparison of the L15* values and IR reflection values in the wavelength region 900±50 nm and in the wavelength region of 1550±20 nm of samples which comprise only a carbon-containing black pigment, and samples which comprise only a flake-form effect pigment. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Reflection Reflection PMC 900 ± 50 nm 1550 ± 20 nm (%) Pigment L*15 value (%) (%) 3.5 Emperor ® 1.1 5.4 5.8 2000 3.5 Spezial 2.3 5.3 5.7 Black ® 6 3.5 Spezial 5.3 4.9 5.9 Black ® 100 18.0 Support Al.sub.2O.sub.3, 45.0 9.5 18.8 about 220 nm, Fe.sub.3O.sub.4 18.0 Support Al.sub.2O.sub.3, 46.2 21.6 12.1 about 150 nm, Fe.sub.3O.sub.4

[0079] The results show that layer composites which have coatings with commercially available colour black can achieve low L*15 values in a stable manner, but the percentage reflection of light in the wavelength regions 900±50 nm and 1550±20 nm is very weak. By contrast, the sole use of flake-form effect pigments used in accordance with the invention (the average geometrical thickness of the supports and the type of iron-containing layer is indicated) still ensure lightness values L* 15 which satisfy the requirement “dark or black”, but lead to significantly improved reflection values in the defined wavelength regions.

Example 2

[0080] The influence of the flake-form effect pigments used in accordance with the invention on the lightness value L*15 and the reflection behaviour of the corresponding layer composite in the defined wavelength regions is investigated when carbon-containing black pigment and flake-form effect pigment are present together in a single layer of the coating. The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Reflection Reflection PMC 900 ± 50 nm 1550 ± 20 (%) Pigment L*15 value (%) nm (%) 3.5 Emperor ® 26.5 7.2 12.6 2000 18.0 Support Al.sub.2O.sub.3, about 220 nm, Fe.sub.3O.sub.4 3.5 Emperor ® 7.7 5.8 6.9 2000 1.8 Support Al.sub.2O.sub.3, about 220 nm, Fe.sub.3O.sub.4 3.5 Emperor ® 25.9 9.6 10.5 2000 9.0 Support Al.sub.2O.sub.3, about 220 nm, Fe.sub.3O.sub.4 9.0 Support Al.sub.2O.sub.3, about 150 nm, Fe.sub.3O.sub.4 1.75 Emperor ® 19.6 8.2 9.1 2000 4.5 Support Al.sub.2O.sub.3, about 220 nm, Fe.sub.3O.sub.4 4.5 Support Al.sub.2O.sub.3, about 150 nm, Fe.sub.3O.sub.4

[0081] The measurement results show that, with increasing proportion by weight of the flake-form effect pigment(s) in the coating, the lightness L*15 increases, but is located in the requisite value range in order to satisfy the requirement “dark or black”. By contrast, the IR reflection values in the target wavelength regions can in some cases be increased considerably compared with a layer composite having a coating which comprises only colour black.

Example 3

[0082] The effect of the ratio of various flake-form effect pigments on the measurement results is investigated when only two flake-form effect pigments which are different from one another, but no carbon-containing black pigment, are present in a layer of the coating. The results are shown in Table 3.

TABLE-US-00003 TABLE 3 Reflection Reflection PMC 900 ± 50 1550 ± 20 (%) Pigment L*15 value nm (%) nm (%) 13.5 Support Al.sub.2O.sub.3, 46.2 13.2 17.0 about 220 nm, Fe.sub.3O.sub.4 4.5 Support Al.sub.2O.sub.3, about 150 nm, Fe.sub.3O.sub.4 9.0 Support Al.sub.2O.sub.3, 46.3 16.4 15.1 about 220 nm, Fe.sub.3O.sub.4 9.0 Support Al.sub.2O.sub.3, about 150 nm, Fe.sub.3O.sub.4 4.5 Support Al.sub.2O.sub.3, 45.8 19.1 13.5 about 220 nm, Fe.sub.3O.sub.4 13.5 Support Al.sub.2O.sub.3, about 150 nm, Fe.sub.3O.sub.4

[0083] The results show that a flake-form effect pigment employed in accordance with the invention having an average geometrical thickness of the support particle in the range from 120 to 150 nm shifts the reflection maximum of the layer composite into the wavelength region 900±50 nm with increasing relative proportion by weight.

[0084] Overall, it can be seen that the best results with respect to the object of the present invention are achieved if equivalent parts by weight of at least two different flake-form effect pigments, optionally combined with a low proportion of carbon-containing black pigment, are employed in a single layer of the coating of the layer composite. Under these conditions, a high to very high increase in the infrared reflection in the target wavelength region compared with a comparative layer composite is obtainable at the same time as good L*15 values.