Method of making retroreflective sheeting and articles

• US 7,458,694 B2
• Filed: 10/10/2007
• Issued: 12/02/2008
• Est. Priority Date: 03/06/2003
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Smith, Kenneth L.
• Primary Examiner(s): Phan; James
• Application Number:
  US11/869,776
• Publication Number:
  US 20080068713A1
• Time in Patent Office: 419 Days
• Field of Search: 359529-530, 264/1.1, 264/1.9
• US Class Current: 359/530
• CPC Class Codes: B29D 11/00605 Production of reflex reflectors
• CPC Class Codes: B29K 2069/00 Use of PC, i.e. polycarbonates or derivatives thereof, as moulding material
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: Y10S 359/90 Methods
• CPC Class Codes: Y10T 428/2457 Parallel ribs and/or grooves

Abstract

The invention relates to a method of making retroreflective sheeting and other articles prepared from casting a moldable synthetic resin onto a tool having a microstructured surface.

Claims

1. A method of making retroreflective sheeting comprising:

providing a tool comprising a PG cube corner microstructured surface with at least one channel;

advancing the tool or a dispensing device in a direction;

casting a moldable resin onto the tool surface such that the channel is substantially parallel to the direction of filling of the channel;

solidifying the resin forming a retroreflective sheeting having a surface comprising cube corner elements; and

removing the sheet from the tool.

2. The method of claim 1 wherein the tool comprises a PG cube cavity channel and the replica of the PG cube cavity channel provides PG cube corner elements.

3. The method of claim 1 wherein the tool comprises PG cube corner microstructure elements.

4. The method of claim 2 wherein the PG cube cavity channel comprises a first planar face and a second structured face.

5. The method of claim 4 wherein the first planar face is a replica of a primary groove face.

6. The method of claim 1 wherein the channel is a primary groove channel.

7. The method of claim 6 wherein the channel comprises a first planar face and second planar face intersecting at a common groove vertex line.

8. The method of claim 1 wherein the channel is a structured channel.

9. The method of claim 8 wherein the structured channel comprises a first face comprising cube corner faces and second face comprising opposing cube corner faces.

10. The method of claim 8 wherein the structured channel comprises the intersection of opposing non-dihedral edges of opposing PG cube corner microstructures.

11. The method of claim 1 wherein the resin is a molten thermoplastic resin.

12. The method of claim 1 wherein the resin is a thermoplastic resin provided in the form of a sheet.

13. The method of claim 1 wherein the resin is provided on a carrier web.

14. The method of claim 1 wherein the tool comprises at least one channel for each row of cube corner microstructures.

15. The method of claim 1 wherein the channel has a ratio of depth relative to the overall height of the microstructured surface and the ratio is greater than about 0.4.

16. The method of claim 15 wherein the channel has a ratio approaching 1.