Retroreflective articles having polymer multilayer reflective coatings

• US 6,243,201 B1
• Filed: 07/26/2000
• Issued: 06/05/2001
• Est. Priority Date: 02/26/1999
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Fleming, Robert J., Lyons, Christopher S., McGrath, Joseph M.
• Primary Examiner(s): Phan, James
• Application Number:
  US09/625,796
• Time in Patent Office: 314 Days
• Field of Search: 359/529, 359/530, 359/534-540, 359/542, 428/174, 428/156, 428/195, 428/201, 428/323, 428/325, 428/327, 428/338, 428/339, 264/1.7, 264/1.9
• US Class Current: 359/530
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G02B 5/128 transparent spheres being embedded in matrix
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A retroreflective article that has a layer of optical elements and a multilayer reflective coating disposed on the optical elements. The reflective coating reflects light back into the optical elements so that it can be returned toward the light source. The multilayer reflective coating has multiple polymer layers and has layers that possess different refractive indices.

Claims

1. A retroreflective article that comprises:

a layer of optical elements; and

a multiple layer reflective coating disposed in optical association with the optical elements, the reflective coating comprising at least two adjacent layers having different refractive indices, at least one of which layers comprises a cured polymer.

2. The retroreflective article of claim 1, wherein the optical elements include microspheres.

3. The retroreflective article of claim 1, wherein the optical elements include cube-corner elements.

4. The retroreflective article of claim 1, wherein the reflective coating has 2 to 200 layers.

5. The retroreflective article of claim 1, wherein at least two adjacent layers of the reflective coating have indices of refraction that differ by at least 0.05.

6. The retroreflective article of claim 1, wherein the reflective coating reflects visible light.

7. The retroreflective article of claim 1, wherein the reflective coating reflects light in a selected wavelength band.

8. The retroreflective article of claim 1, wherein the reflective coating has a first portion and a second portion, the first portion of the reflective coating having adjacent layers that have different indices of refraction and optical thicknesses selected to redirect light in a first selected wavelength band from a first area of the retroreflective article, and the second portion of the reflective coating having adjacent layers that have different indices of refraction and optical thicknesses selected to redirect light in a second selected wavelength band from a second area of the retroreflective article.

9. The retroreflective article of claim 8, wherein the first and second portions of the reflective coating form a character, numeral, or indicium.

10. The retroreflective article of claim 1, further comprising an adhesion promoter disposed between the layer of optical elements and the reflective coating.

11. The retroreflective article of claim 10, wherein the adhesion promoter is a silane coupling agent.

12. The retroreflective article of claim 1, wherein the reflective coating further comprises a non-polymer layer that is a metal oxide layer, an inorganic dielectric layer, an organometallic layer, or a ceramic layer.

13. The retroreflective article of claim 12, wherein the non-polymer layer is disposed between the layer of optical elements and the cured polymer layer.

14. The retroreflective article of claim 12, wherein the non-polymer layer is disposed between two polymer layers.

15. The retroreflective article of claim 1, wherein the reflective coating further comprises alternating layers of a polymeric material that has a first index of refraction and a non-polymer material that has a second index of refraction different from the first index of refraction, wherein the non-polymer material comprises a metal oxide, inorganic dielectric, organometallic, or ceramic material.

16. The retroreflective article of claim 1, wherein the cured polymer layer is formed by condensing and curing a pre-polymer vapor.

17. The retroreflective article of claim 1, wherein the cured polymer is formed from one or more of acrylates, methacrylates, acrylamides, methacrylamides, vinyl ethers, maleates, cinnamates, styrenes, olefins, vinyls, epoxides, silanes, melamines, hydroxy functional monomers, and amino functional monomers.