Angular brightness microprismatic retroreflective film or sheeting incorporating a syndiotactic vinyl aromatic polymer

• US 6,274,221 B2
• Filed: 01/29/1999
• Issued: 08/14/2001
• Est. Priority Date: 01/29/1999
• Status: Expired due to Term

• Current Assignee: 3M Company, 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Smith, Kenneth L., Tabar, Ronald J., Ojeda, Jaime R.
• Primary Examiner(s): Copenheaver, Blaine
• Assistant Examiner(s): Chevalier, Alicia
• Application Number:
  US09/240,342
• Publication Number:
  US 20010008679A1
• Time in Patent Office: 928 Days
• Field of Search: 428/141, 428/156, 359/529, 526/335, 526/340, 526/346, 525/70, 525/98
• US Class Current: 428/141
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

A novel microprismatic retroreflective film or sheeting is provided which comprises a transparent semicrystalline polymer. The microprismatic retroreflective film or sheeting of the present invention offers superior retroreflective brightness at large angles of incidence and at large observational angles. Syndiotactic vinyl aromatic polymers, especially syndiotactic polystyrene and copolymers thereof, are preferred semicrystalline polymers, as they impart good dimensional stability and resistance to moisture, and can be made resistant to UV radiation. Signing materials comprising these microprismatic retroreflective films provide improved performance for off-angle illumination and viewing in traffic control and other signing applications.

Claims

1. A transparent retroreflective film comprising a polymer having an ordered array of integrally formed, interconnected, retroreflecting elements of substantially common shape said film, redirects light towards its originating source with high efficiency due to total internal reflection of light falling on the retroreflecting elements, wherein the film comprises:

a syndiotatic polymer derived from a vinyl aromatic monomer to provide the polymer of the retroreflective film,

wherein the film has a retroreflective surface having cube-cornered geometry.

2. The film of claim 1, wherein the syndiotactic polymer is a transparent semicrystalline polymer.

3. The film of claim 1, wherein the syndiotactic polymer comprises at least 80% by weight of styrene moieties.

4. The film of claim 3, wherein the syndiotactic polymer further comprises at least 5% by weight of para-methylstyrene moieties.

5. The film of claim 1, wherein the syndiotactic polymer is syndiotactic polystyrene.

6. The film of claim 1, having at least one microprismatic surface.

7. The film of claim 1, wherein the syndiotactic polymer has at least 20% by weight of syndiotactic chain segments.

8. The film of claim 1, wherein the syndiotactic polymer has between 30% and 98% by weight of syndiotactic chain segments.

9. The film of claim 1, wherein the syndiotactic polymer has at least 85% and 95% by weight of syndiotactic chain segments.

10. The film of claim 1, optionally comprising between about 0.5 and 2.0 parts by weight of a UV absorbing material per 100 parts by weight of the syndiotactic polymer.

11. The film of claim 1, further comprising an antioxidant.

12. The film of claim 11, wherein the antioxidant is present in an amount of between about 1×

10<sup>−

4</sup> and about 2 parts by weight per 100 parts by weight of the syndiotactic polymer.

13. The film of claim 11, wherein the antioxidant is present in an amount of between about 0.001 and about 1 part by weight per 100 parts by weight of the syndiotactic polymer.

14. The film of claim 11, wherein the antioxidant is present in an amount of between about 0.01 and about 0.5 part by weight per 100 parts by weight of the syndiotactic polymer.

15. The film of claim 11, wherein the antioxidant is a hindered phenolic resin.

16. The film of claim 1, wherein the retroreflective elements provide brightly reflected light at observation angles from about 0.33°

to about 0.5°

.

17. A sign comprising the film of claim 1.