Visibly transparent infrared reflecting film with color masking

• US 5,233,465 A
• Filed: 05/27/1992
• Issued: 08/03/1993
• Est. Priority Date: 05/27/1992
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Wheatley, John A., Schrenk, Walter J.
• Primary Examiner(s): Ryan, Patrick J.
• Assistant Examiner(s): LAM, CATHY FONG FONG
• Application Number:
  US07/888,705
• Time in Patent Office: 433 Days
• Field of Search: 428/30, 428/212, 428/213, 428/215, 428/220, 428/409, 428/411.1, 428/204, 428/206, 428/332, 428/916, 428/913.3, 428/688, 428/500, 428/515, 359/588, 359/589, 359/359
• US Class Current: 359/359
• CPC Class Codes: G02B 5/282 reflecting for infrared and transparent for visible light, e.g. heat reflectors, laser protection

Abstract

A polymeric multilayered film which reflects wavelengths of light in the infrared region of the spectrum while being substantially transparent to wavelengths of light in the visible spectrum without the effects of visibly perceived iridescent color is provided. The polymeric multilayered infrared reflecting film comprises at least two diverse, substantially transparent polymeric materials, with the layers having an optical thickness of between 0.09 μm and 0.45 μm and the polymeric materials having a different index of refraction such that light is reflected in the infrared portion of the spectrum. A color masking film is associated with the polymeric film which reflects light substantially uniformly over the visible portion of the spectrum to eliminate perceived iridescent color.

Claims

1. A substantially colorless polymeric multilayered film having at least two major surfaces and which reflects a majority of light in the infrared region of the spectrum while transmitting a majority of light in the visible region of the spectrum comprising, multiple alternating layers of at least two diverse, substantially transparent polymeric materials which differ in refractive index by at least about 0.03, said layers having an optical thickness of between about 0.09 μ

m and 0.45 μ

m and each of said polymeric materials having a different index of refraction such that said film reflects light in the infrared portion of the spectrum, and means associated with said film for masking any iridescent visible color reflected from said layers such that there is an absence of visibly perceived color reflected from said film, said color masking means comprise a sufficient number of alternating layers of substantially transparent diverse polymeric materials, a substantial majority of said layers having an optical thickness of not less than 0.45 μ

m or not greater than 0.09 μ

m.

2. The substantially colorless polymeric multilayered film of claim 1 wherein said film reflects light in the ultraviolet region of the spectrum.

3. The substantially colorless multilayered film of claim 1 in which said film includes first (A), second (B), and third (C) diverse polymeric materials of alternating layers having a repeating pattern ABCB.

4. The substantially colorless polymeric multilayered film of claim 3 in which said first polymeric material is polystyrene, said second polymeric material is a copolymer of styrene and methyl methacrylate, and said third polymeric material is polymethyl methacrylate.

5. The substantially colorless polymeric multilayered film of claim 3 in which said first polymeric material is polycarbonate, said second polymeric material is a copolymer of styrene and methyl methacrylate, and said third polymeric material is polymethyl methacrylate.

6. The substantially colorless multilayered film of claim 1 in which said film includes first (A) and second (B) polymeric materials of alternating layers having a repeating pattern ABAB.

7. The substantially colorless polymeric multilayered film of claim 6 in which said first polymeric material is polystyrene and said second polymeric material is polymethylmethacrylate.

8. The substantially colorless polymeric multilayered film of claim 1 wherein said color masking means comprise a masking film which reflects light substantially uniformly over the visible portion of the spectrum.

16. The substantially colorless polymeric multilayered film of claim 1 wherein said color masking means are located on one or both of said major surfaces of said body.

17. The substantially colorless polymeric multilayered film of claim 1 wherein said color masking means are located between interior layers of said body.

18. The substantially colorless polymeric multilayered film of claim 1 in which there is a layer thickness gradient across the thickness of said film.

19. The substantially colorless polymeric multilayered film of claim 17 in which said layer thicknesses increase monotonically across the thickness of said film.

20. The substantially colorless polymeric multilayered film of claim 1 in which at least 70% of said light in the visible region of the spectrum is transmitted through said film.

9. A substantially colorless polymeric multilayered film having at least two major surfaces and which reflects a majority of at least two major surfaces and which reflects a majority of light in the infrared region of the spectrum while transmitting a majority of light in the visible region of the spectrum comprising, multiple alternating layers of first (A), second (B), and third (C) diverse substantially transparent polymeric materials which differ in refractive index by at least about 0.03, said layers having an optical thickness of between about 0.09 μ

m and 0.45 μ

m and each of said polymeric materials having a different index of refraction such that said film reflects light in the infrared portion of the spectrum, and

means associated with said film for masking any iridescent visible color reflected from said layers such that there is an absence of visibly perceived color reflected from said film.

10. The substantially colorless polymeric multilayered film of claim 9 wherein said alternating layers of polymeric materials comprise polycarbonate and polymethylmethacrylate.

11. The substantially colorless polymeric multilayered film of claim 9 wherein said alternating layers of polymeric materials comprise polystyrene and polymethylmethacrylate.

12. The substantially colorless polymeric multilayered film of claim 9 wherein said color masking means is laminated to said film.

13. The substantially colorless polymeric multilayered film of claim 9 wherein said color masking means comprise a substantially colorless metal oxide or metal halide film having sufficient reflectance to mask the visible iridescent color effects of the infrared reflecting film.

14. The substantially colorless polymeric multilayered film of claim 13 wherein said color masking means is deposited on said film.

15. The substantially colorless polymeric multilayered film of claim 9 wherein said color masking means comprise a sufficient number of alternating layers of substantially transparent diverse polymeric materials, a substantial majority of said layers having an optical thickness of not less than 0.45 μ

m or not greater than 0.09 μ

m.