Retroreflective material with improved angularity

• US 5,138,488 A
• Filed: 09/10/1990
• Issued: 08/11/1992
• Est. Priority Date: 09/10/1990
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Szczech, Theodore J.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Phan, James
• Application Number:
  US07/579,566
• Time in Patent Office: 701 Days
• Field of Search: 350/97, 350/102, 350/103, 350/109
• US Class Current: 359/529
• CPC Class Codes: B29C 65/08 using ultrasonic vibrations non-plastics element to plastics elements B29C65/645
• CPC Class Codes: B29K 2001/12 Cellulose acetate
• CPC Class Codes: B29K 2001/14 Cellulose acetate-butyrate
• CPC Class Codes: B29K 2995/003 Reflective
• CPC Class Codes: G02B 5/122 cube corner, trihedral or triple reflector type
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet

Abstract

The present invention provides an improved cube-corner retroreflective article that exhibits a wide range of retroreflective angularity in multiple viewing planes. The present invention provides cube-corner retroreflective elements having a decreased size, as measured by the height of the cube corner, thereby decreasing the amount of canting required to achieve a given angularity. Alternatively, angularity can be enhanced by leaving the degree of canting constant and decreasing the size of the cube corner.

Claims

1. A retroreflective article comprising:

at least one pair of cube-corner retroreflective elements, comprising three triangular and substantially mutually perpendicular lateral faces that meet at an apex, said mutually perpendicular lateral faces of each element being defined at their bases by linear edges that lie in a common base plane;

adjacent pairs of said elements rotated 180 degrees with respect to one another;

each retroreflective element having a height "h", measured from the base plane to the apex of the element along a line perpendicular to the base plane, h being less than about 150 μ

m; and

the optical axis of each element of the pair being tilted toward one edge of that element from the line perpendicular to said common base plane at an angle, alpha, wherein alpha is about 2°

to 5°

.

2. The retroreflective article of claim 1 in which the height "h" is about 25 μ

m to 100 μ

m.

3. The retroreflective article of claim 2 in which the height "h" is about 50 μ

m to 100 μ

m.

4. The retroreflective article of claim 1 wherein at least one of said elements has half groove angle errors of about 20 arc minutes or less distributed in a random pattern throughout.

5. The retroreflective article of claim 4 wherein at least one of said elements have errors of about 5 arc minutes or less.

6. The retroreflective article of claim 1 wherein said pairs of elements are arranged in an array of rows and columns.

7. The retroreflective article of claim 1 further including a backing layer.

8. The retroreflective article of claim 1 wherein said elements consist of a polymeric material having an index of refraction of about 1.5, the angle, alpha is about 2°

to 5°

, and the height, "h" is about 25 μ

m to 100 μ

m.

9. The retroreflective article of claim 1 wherein the optical axes of the cube-corner retroreflective elements in adjacent pairs are coplanar.