Totally internally reflecting thin, flexible film

• US 5,056,892 A
• Filed: 01/30/1990
• Issued: 10/15/1991
• Est. Priority Date: 11/21/1985
• Status: Expired

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Cobb, Sanford Jr.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Phan, James
• Application Number:
  US07/472,621
• Time in Patent Office: 623 Days
• Field of Search: 350/286, 350/287, 350/276 R, 350/616, 350/176, 350/167, 350/103, 350/104, 350/106, 350/109, 362/32, 362/339, 362/337
• US Class Current: 359/831
• CPC Class Codes: F21V 2200/40 of hollow light guides
• CPC Class Codes: F21V 5/002 using microoptical elements for redirecting or diffusing light
• CPC Class Codes: F24S 23/10 Prisms
• CPC Class Codes: F24S 23/80 having discontinuous faces
• CPC Class Codes: G02B 3/005 arranged along a single direction only, e.g. lenticular sheets G02B3/0043 takes precedence
• CPC Class Codes: G02B 5/02 Diffusing elements; Afocal elements
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 5/12 Reflex reflectors
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type
• CPC Class Codes: Y02E 10/40 Solar thermal energy, e.g. solar towers

Abstract

A thin, flexible film made of a transparent polymeric material including a structured surface and an opposite smooth surface, wherein light striking either surface, within certain angular ranges, is totally internally reflected. The structured surface includes a linear array of miniature substantially right angled isosceles prisms arranged side-by-side to form a plurality of peaks and grooves. In addition, the perpendicular sides of the prims make an angle of approximately 45° with the smooth surface, and when the film is curled the smooth surface lies in a smooth continuous arcuate curve without materially affecting the performance of the film. Because of the film'"'"'s flexibility and its ability to totally internally reflect light, it may be utilized in a variety of ways, for example, as a collector of solar energy or as a light conduit. The performance of the film may be manipulated to permit controlled light leakage.

Claims

1. A thin, flexible film of a transparent polymeric material, comprising a structured surface on one side and a smooth surface opposite said structured surface on the other side, said structured surface includes a linear array of miniature isosceles prisms having substantially perpendicular sides arranged side-by-side to form a plurality of peaks and grooves said film having at least 40 of said prisms per inch, the perpendicular sides of said prisms make an angle of approximately 45°

with said smooth surface opposite said structured surface, said film being capable of being curled such that said smooth surface lies in a smooth continuous arcuate curve having a diameter of approximately 18 inches.

2. The film defined in claim 1, wherein the film does not have sufficient strength to be self-supporting.

3. The film defined in claim 1, wherein said transparent polymeric material is polycarbonate.

4. The film defined in claim 1, wherein said transparent polymeric material is acrylic.

5. The film defined in claim 1, wherein incident light striking the smooth surface within certain angular ranges is totally internally reflected.

6. The film defined in claim 1, wherein incident light striking the structured surface within certain angular ranges is totally internally reflected.

7. The film defined in claim 1 wherein said film has a thickness of approximately 0.015 of an inch and about 70 prisms per inch so that when said film is curled said smooth surface lies in a smooth continuous arcuate curve without any discernible discontinuities.

8. A thin, flexible film of a transparent polymeric material, comprising a structured surface on one side and a smooth surface opposite said structured surface on the other side, said structured surface includes a linear array of miniature isosceles prisms having substantially perpendicular sides arranged side-by-side to form a plurality of peaks and grooves, the perpendicular sides of said prisms make an angle of approximately 45°

with said smooth surface opposite said structured surface, said film being capable of being curled such that said smooth surface lies in a smooth continuous arcuate curve having a diameter of approximately 18 inches and said film does not have sufficient strength to be self-supporting.