Prismatic retroreflective article and method

• US 7,195,360 B2
• Filed: 12/28/2004
• Issued: 03/27/2007
• Est. Priority Date: 12/28/2004
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: David, Moses M., Kirk, Seth M., Bacon, Chester A. Jr., Owusu, Osei A., Currens, Michael D.
• Primary Examiner(s): Cherry; Euncha
• Application Number:
  US11/023,857
• Publication Number:
  US 20060139754A1
• Time in Patent Office: 819 Days
• Field of Search: 359/515, 359/516, 359/518, 359/528, 359/529, 359/530, 359/531, 359/541, 359547-553
• US Class Current: 359/529
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet

Abstract

A prismatic retroreflective article has a transparent body portion and a layer of internally reflecting cube-corner optical elements having an open air-exposed rear surface at least a portion of which is more hydrophobic, more oleophobic, or both more hydrophobic and more oleophobic than the underlying cube-corner optical element. The article may be made by providing a transparent body portion bearing a layer of internally reflecting open air-exposed cube-corner optical elements; treating or coating at least a portion of the cube-corner elements to make the treated or coated portion more hydrophobic, more oleophobic, or both more hydrophobic and more oleophobic than the underlying cube-corner optical elements; and leaving such treated or coated portion exposed to the open air.

Claims

1. A prismatic retroreflective article comprising a transparent body portion and a layer of internally reflecting cube-corner optical elements having an open air-exposed rear surface at least a portion of which is more hydrophobic, more oleophobic, or both more hydrophobic and more oleophobic than the underlying cube-corner optical element.

2. A retroreflective article according to claim 1, comprising cube-corner optical element rear surfaces bearing a transparent conformal coating.

3. A retroreflective article according to claim 2, wherein the cube-corner elements have a characteristic height and the coating has a thickness less than about 10% of the cube-corner optical element characteristic height.

4. A retroreflective article according to claim 2, wherein the cube-corner elements have a characteristic height and the coating has a thickness less than about 5% of the cube-corner optical element characteristic height.

5. A retroreflective article according to claim 2, wherein the coating has a thickness less than about 3 μ

m.

6. A retroreflective article according to claim 1, wherein water or mineral oil will bead up rather than spreading when applied to the cube-corner optical elements.

7. A retroreflective article according to claim 1, wherein water and mineral oil will bead up rather than spreading when applied to the cube-corner optical elements.

8. A retroreflective article according to claim 1, comprising cube-corner optical elements having an increased number of fluorine or silicon atoms at the exposed cube-corner element surface compared to the underlying cube-corner optical element.

9. A retroreflective article according to claim 1, further comprising a support on which the retroreflective article is mounted while leaving the cube-corner optical elements exposed to the open air.

10. A retroreflective article according to claim 9, wherein the support comprises a fabric.

11. A method for making a prismatic retroreflective article comprising providing a transparent body portion bearing a layer of internally reflecting open air-exposed cube-corner optical elements;

treating or coating at least a portion of the cube-corner optical elements to make the treated or coated portion more hydrophobic, more oleophobic, or both more hydrophobic and more oleophobic than the underlying cube-corner optical elements; and

leaving such treated or coated portion exposed to the open air.

12. A method according to claim 11, comprising treating the cube-corner optical elements by condensing and polymerizing vapors of a fluorochemical acrylate, fluorochemical methacrylate, acrylic-functional siloxane or methacrylic-functional siloxane on the surface of the cube-corner elements.

13. A method according to claim 11, comprising treating the cube-corner optical elements by coating them with a fluoro/silane-containing ceramer hardcoat;

a transparent ceramer hardcoat followed by a solvent-borne fluorine-containing or silicon-containing antisoiling layer;

a self-assembling fluorine- or silicon-containing monomolecular antisoiling layer;

a solution of a low surface energy polymer;

a solution containing a silane coupling agent;

a polymerized siloxane;

a silazane;

or an organometallic material.

14. A method according to claim 11, comprising treating the cube-corner optical elements with fluorine gas, fluorine atoms or silicon atoms using plasma, glow discharge or corona discharge.

15. A method according to claim 14, comprising treating the cube-corner optical elements with a perfluoroalkane.

16. A method according to claim 15, wherein the perfluoroalkane comprises perfluoropropane or perfluorobutane.

17. A method according to claim 14, comprising treating the cube-corner optical elements with a silane.

18. A method according to claim 17, wherein the silane comprises tetramethylsilane.

19. A method according to claim 11, further comprising applying an adhesion promoter to the layer of optical elements before treating or coating them.

20. A method according to claim 11, further comprising mounting the article on a support while leaving the cube-corner optical elements exposed to the open air.

21. A method according to claim 20, wherein the support comprises a fabric.