Totally internally reflecting thin, flexible film

• US 4,906,070 A
• Filed: 07/12/1988
• Issued: 03/06/1990
• Est. Priority Date: 11/21/1985
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Cobb, Sanford Jr.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Kachmarik, Ronald M.
• Application Number:
  US07/218,087
• Time in Patent Office: 602 Days
• Field of Search: 350/286, 350/287, 350/276 R, 350/616, 350/617, 350/167, 350/168, 350/103, 350/104, 350/106, 350/109, 362/32, 362/339, 362/337
• US Class Current: 359/834
• 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: G02B 5/12 Reflex reflectors
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00
• CPC Class Codes: G02B 6/24 Coupling light guides
• CPC Class Codes: G02B 6/3807 Dismountable connectors, i.e. comprising plugs
• 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 prisms 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, wherein 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 less than 3 inches.

2. The film defined in claim 1, wherein said isosceles prisms are micro in size, at least 40 per inch.

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

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

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

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

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

8. 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.

9. A light conduit for transporting light, comprising a thin, flexible film of a transparent polymeric material including a structured surface on one side and a smooth surface opposite said structured surface on the other side, said structured surface having 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, and said film is formed into a tubular configuration so that said smooth surface lies in a smooth continuous arcuate curve, whereby light entering the conduit, within certain angular ranges, is totally internally reflected as it travels along the conduit.

10. The light conduit defined in claim 9, wherein the corners of said prisms of said structured surface are not optically sharp, so that the light conduit acts as an illuminator by allowing some of the light entering said conduit to escape through the film without being totally internally reflected.

11. The light conduit defined in claim 9, wherein the perpendicular sides of said prisms of said structured surface are not optically smooth, so that the light conduit acts as an illuminator by allowing some of the light entering said conduit to escape through the film without being totally internally reflected.

12. The light conduit defined in claim 9, wherein said peaks are rounded to permit controlled light leakage defined in accordance with the ratio r/ρ

, where r is the approximate radius of the round peaks and ρ

is the groove period.

13. 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 isoceles 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 less than 18 inches wherein said peaks are rounded to permit controlled light leakage in accordance with the ratio r/ρ

where r is the approximate radius of the round peaks and ρ

is the groove period.