All-polymeric ultraviolet light reflecting film

• US 5,540,978 A
• Filed: 05/11/1994
• Issued: 07/30/1996
• Est. Priority Date: 02/25/1992
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Schrenk, Walter J.
• Primary Examiner(s): KILIMAN, LESZEK B
• Application Number:
  US08/240,970
• Time in Patent Office: 811 Days
• Field of Search: 428/421, 428/522, 428/422, 428/212, 428/213, 428/332, 428/333, 428/339, 359/586
• US Class Current: 428/212
• CPC Class Codes: B32B 2307/416 Reflective
• CPC Class Codes: B32B 2551/00 Optical elements
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/304 comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• CPC Class Codes: B32B 27/308 comprising acrylic (co)polymers
• CPC Class Codes: B32B 7/023 Optical properties
• CPC Class Codes: F24S 23/81 flexible F24S23/715, F24S23/745 take precedence
• CPC Class Codes: G02B 1/04 made of organic materials, e.g. plastics G02B1/08 takes precedence
• CPC Class Codes: G02B 5/287 comprising at least one layer of organic material
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: Y02B 10/20 Solar thermal
• CPC Class Codes: Y02E 10/40 Solar thermal energy, e.g. solar towers
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/2495 Thickness [relative or absolute]
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/261 In terms of molecular thickness or light wave length
• CPC Class Codes: Y10T 428/269 including synthetic resin or polymer layer or component
• CPC Class Codes: Y10T 428/3154 Of fluorinated addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

Abstract

An all-polymeric ultraviolet light reflective film which is lower in cost than previously used reflector materials, is weather resistant, and which does not absorb significant amounts of solar ultraviolet energy is provided. The film includes a sufficient number of alternating layers of at least first and second diverse polymeric materials which have an average percent transmission of greater than about 50% between wavelengths of 300-400 nm. A substantial majority of the individual layers of the film have optical thicknesses in the range where the sum of the optical thicknesses in a repeating unit of the polymeric materials is between about 0.15 μm to about 0.228 μm, and the first and second polymeric materials differ from each other in refractive index by at least about 0.03 in the wavelength range of from about 300-400 nm. The reflective film is useful as a reflective material in solar detoxification systems, as a protective material in indoor and outdoor lighting systems, as a UV mirror in the fields of medical imaging, astronomical telescopes, and microscopy or in chemical reactions using UV radiation.

Claims

1. An ultraviolet light reflective all-polymeric film of at least first and second diverse polymeric materials which do not absorb significant amounts of ultraviolet radiation, said at least first and second polymeric materials are selected from the group consisting of polymethyl methacrylate, polyvinylidene fluoride, polychlorotrifluoroethylene, and polymethylpentene-1, the film comprising a sufficient number of alternating layers of at least said first and second polymeric materials which form predetermined repeating units such that at least 30% of ultraviolet light of a wavelength of between about 300-400 nm incident on said film is reflected, said first and second polymeric materials having an average percent transmission of greater then about 50% between wavelengths of 300-400 nm, a substantial majority of the individual layers of said film having optical thicknesses in the range where the sum of the optical thicknesses in one of said repeating units of said polymeric materials is between about 0.15 μ

m to about 0.228 μ

m, and wherein said first and second polymeric materials differ from each other in refractive index by at least about 0.03 in the wavelength range of from about 300-400 nm.

2. The ultraviolet light reflective polymeric film of claim 1 in which said individual layers have optical thicknesses of between about 0.07 μ

m to about 0.11 μ

m.

3. The ultraviolet light reflective polymeric film of claim 1 in which said first polymeric material is polyvinylidene fluoride and said second polymeric material is polymethyl methacrylate.

4. The ultraviolet light reflective polymeric film of claim 1 in which said polymeric film is laminated to or coextruded with an infrared light reflecting body.

5. The ultraviolet light reflective polymeric film of claim 1 in which said film comprises at least 200 layers.

6. The ultraviolet light reflective polymeric film of claim 1 in which at least 80% of ultraviolet light of a wavelength of between about 300-400 nm incident on said film is reflected.

7. The ultraviolet light reflective polymeric film of claim 1 in which said polymeric film includes first, second, and third diverse polymeric materials of alternating layers in a repeating unit ABCB.

8. The ultraviolet light reflective polymeric film of claim 1 in which said polymeric film includes first, second, and third diverse polymeric materials of alternating layers in a repeating unit ABC.

9. The ultraviolet light reflective polymeric film of claim 1 in which said polymeric film is laminated or coextruded with a transparent substrate material.

10. The ultraviolet light reflective polymeric film of claim 1 in which said polymeric film is laminated to or coextruded with a visible light reflecting body.

11. The ultraviolet light reflective polymeric film of claim 1 in which the film includes protective skin layers on both major exterior surfaces of said film.

12. The ultraviolet light reflective polymeric film of claim 11 in which said protective skin layers comprise polyvinylidene fluoride.