Retroreflective articles having polymer multilayer reflective coatings

• US 6,172,810 B1
• Filed: 02/26/1999
• Issued: 01/09/2001
• 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:
  US09/259,100
• Time in Patent Office: 683 Days
• Field of Search: 359/529, 359/530, 359/536, 359/538-540, 359/543, 359/584-589
• US Class Current: 359/529
• 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 reflective coating that is disposed in optical association with the optical elements, the reflective coating comprising a plurality of layers wherein (i) at least two adjacent layers have different refractive indices, and (ii) the reflective coating includes one or more polymer layers that each have an average thickness that is less than about 10% of an average size of the optical elements,

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.

2. The retroreflective article of claim 1, wherein the first and second portions of the reflective coating form a character, numeral, or indicium.

3. A retroreflective article that comprises:

a layer of optical elements; and

a reflective coating that is disposed in optical association with the optical elements, the reflective coating comprising a plurality of layers wherein (i) at least two adjacent layers have different refractive indices, and (ii) the reflective coating includes one or more polymer layers that each have an average thickness that is less than about 10% of an average size of the optical elements; and

an adhesion promoter disposed between the layer of optical elements and the reflective coating.

4. The retroreflective article of claim 3, wherein the adhesion promoter is a silane coupling agent.