Cube corner sheetiing mold and of making the same

• US 20020028263A1
• Filed: 09/27/2001
• Published: 03/07/2002
• Est. Priority Date: 07/02/1997
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Erwin, Robert L., Luttrell, Dan E., Smith, Kenneth L., Benson, Gerald M.
• Granted Patent: US 6,386,855 B1
• Time in Patent Office: Days
• US Class Current: 425/193
• CPC Class Codes: B29D 11/00625 Moulds for reflex reflectors moulds for plastic articles in general B29C33/00
• CPC Class Codes: Y10S 425/03 Laminated mold

Abstract

Laminae suitable for use in molds for forming retroreflective cube corner elements and methods for making such laminae are disclosed. A representative lamina includes a first row of cube corner elements disposed in a first orientation and a second row of optically opposing cube corner elements disposed. The working surface of a lamina is provided with a plurality of cube corner elements formed by the optical surfaces defined by three groove sets. Opposing first and second groove sets are formed in the working surface of a lamina. The first groove set forms a plurality of structures having first and second optical surfaces disposed in mutually perpendicular planes that intersect along a reference edge. The second groove set forms a corresponding plurality of structures on the opposite side of the lamina. A third groove is formed in the working surface of the lamina along an axis substantially perpendicular to the axes of the grooves of the first and second groove sets. The surfaces of the third groove intersect the surfaces of the plurality of structures in substantially mutually perpendicular planes to define a plurality of cube corner elements. A plurality of such laminae can be assembled to form a mold useful in the manufacture of retroreflective products such as cube corner sheeting.

Claims

1. A lamina suitable for use in a mold for use in forming retroreflective cube corner articles, the lamina having opposing first and second major surfaces defining therebetween a first reference plane, the lamina further including a working surface connecting the first and second major surfaces, the lamina comprising:

two rows of cube corner elements in the working surface, at least one such row comprising a plurality of nonidentical cube corner elements.

2. The lamina of claim 1, wherein the two rows of cube corner elements define therebetween a groove extending along the working surface of the lamina.

3. The lamina of claim 2, wherein at least one of the two rows of cube corner elements further define a set of parallel grooves.

4. The lamina of claim 3, wherein the set of parallel grooves comprises grooves of differing included angles.

5. The lamina of claim 3, wherein the set of parallel grooves comprises grooves having a nonuniform groove spacing.

6. A mold comprising the lamina of claim 1.

7. A cube corner article formed as a replica of the mold of claim 6.

8. A method of making a lamina suitable for use in a mold for use in forming retroreflective cube corner articles, the method comprising:

providing a lamina having opposing first and second major surfaces; and

forming a first, second, and third groove set in the lamina to define two rows of cube corner elements extending therealong;

wherein the forming step is performed with the lamina registered in one position.

9. The method of claim 8, wherein the first groove set comprises a first plurality of parallel grooves, and wherein the second groove set comprises a second plurality of parallel grooves.

10. The method of claim 9, wherein the third groove set consists essentially of a single groove.

11. A method of making a mold for use in forming retroreflective cube corner articles, comprising making laminae according to the method of claim 8 and assembling the laminae together.

12. A method of making a retroreflective article, comprising making a mold according to claim 11 and forming the retroreflective article from the mold by at least one replication step.