Weather-resistant film for the yellow coloration of retro-reflective moulded bodies

1. A foil comprising at least one polymethyl methacrylate layer colored with a yellow anthraquinone dye, where the chromaticity coordinates (x;y) in the CIE1931 standard colorimetric system of the polymethyl methacrylate layer are preferably within the range of 0.4≦x≦0.54 and 0.44≦y≦0.54, wherein the concentration of the yellow dye in the polymethyl methacrylate layer is at least 3% by weight, based on the total weight of the polymethyl methacrylate layer.

2. A foil according to claim 1 , wherein the polymethyl methacrylate layer comprises at least one impact modifier.

3. A foil according to claim 2 , wherein the impact modifier is obtained via emulsion polymerization.

4. The foil according to claim 1 , wherein the polymethyl methacrylate layer comprises a molding composition comprising

A) from 10 to 90% by weight of a coherent hard phase with a glass transition temperature above 70° C., encompassing

a) from 80 to 100% by weight (based on A) of methyl methacrylate and

b) from 20 to 0% by weight of a lower alkyl acrylate, and

B) from 90 to 10% by weight of a tough phase distributed within the hard phase and having a glass transition temperature below −10° C., and an average tough-phase particle size below 130 nm and a tough-phase particle-size polydispersity of less than 0.5, comprising

c) at least 50% by weight (based on B) of a lower alkyl acrylate,

d) from 0.5 to 5% by weight of a graft-linking agent or of a crosslinking monomer having three or more ethylenically unsaturated radicals capable of free-radical polymerization.

5. The foil according to claim 4 , wherein at least 15% by weight of the hard phase has covalent linking to the tough phase.

6. The foil according to claim 1 , wherein the polymethyl methacrylate layer comprises a polymethyl methacrylate molding composition that is obtained via polymerization of one or more monomer mixtures that comprises one or more monomers having groups that absorb UV radiation.

7. The foil according to claim 1 , wherein the chromaticity coordinates of the yellow anthraquinone dye (x;y) to CIE 1931 Standard Colorimetric Systems are within the range of 0.4≦x≦0.54 and 0.44≦y≦0.54.

8. The foil according to claim 1 , wherein the yellow anthraquinone dye is soluble in an organic solvent.

9. The foil according to claim 1 , wherein the yellow dye is Solvent Yellow 163.

10. The foil according to claim 1 , wherein the thickness of the polymethyl methacrylate layer is in the range from 50 μm to 150 μm.

11. The foil according to claim 1 , wherein the foil has been bonded to a retroreflective substrate.

12. The foil according to claim 1 , further comprising a scratch-resistant layer comprising a highly crosslinked plastic arranged on a surface of the foil.

13. The foil according to claim 1 , wherein the modulus of elasticity of the polymethyl methacrylate layer is in the range from 500 to 3200 MPa.

14. The foil according to claim 1 , wherein the weathering resistance of the polymethyl methacrylate layer is at least 2200 hours to ASTM D4956-95, section 7.4.

15. A process for production of a foil according to claim 1 , comprising

mixing a yellow anthraquinone dye with a polymethyl methacrylate molding composition to form a material, and

extruding the material.

16. A retroreflective molding comprising at least one foil according to claim 1 .

17. A traffic sign comprising a foil according to claim 1 .

18. The foil according to claim 1 , wherein the chromaticity coordinates are within the range of 0.47≦x≦0.52 and 0.47≦y≦0.51.

19. The foil according to claim 14 , wherein the yellow anthraquinone dye is 1,8-bis(phenylthio)-anthraquinone.