WO2002008808A1 - Feuille en plastique multicouche pour conducteur de lumiere - Google Patents

Feuille en plastique multicouche pour conducteur de lumiere Download PDF

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Publication number
WO2002008808A1
WO2002008808A1 PCT/US2001/016523 US0116523W WO0208808A1 WO 2002008808 A1 WO2002008808 A1 WO 2002008808A1 US 0116523 W US0116523 W US 0116523W WO 0208808 A1 WO0208808 A1 WO 0208808A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
layer
light pipe
layers
refraction
Prior art date
Application number
PCT/US2001/016523
Other languages
English (en)
Inventor
Donald A. Maclennan
Original Assignee
Fusion Lighting, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fusion Lighting, Inc. filed Critical Fusion Lighting, Inc.
Publication of WO2002008808A1 publication Critical patent/WO2002008808A1/fr

Links

Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02Physical, chemical or physicochemical properties
    • B32B7/023Optical properties
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B1/00Layered products having a general shape other than plane
    • B32B1/08Tubular products
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0096Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the lights guides being of the hollow type

Definitions

  • the invention relates generally to light distribution systems such as light pipes. More particularly, the invention relates to a novel plastic sheet material for a light pipe.
  • the present invention relates to the type of light pipes disclosed in PCT Publication No. WO 00/43815 (the '815 Publication), which is herein incorporated by reference in its entirety.
  • U.S. Patent No. 5,882,774 discloses a multi-layer optical film and U.S. Patent No. 5,661 ,839 discloses a light pipe which utilizes the multi-layer optical film.
  • the multi-layerfilm consists of numerous quarterwave stacks which collectively provide a high reflectivity over a wide wavelength range and also over all angles of incidence.
  • Each quarterwave stack consists of a low and high index pair of film layers, where each layer pair has a combined optical thickness of 1/2 the center wavelength of the band it is designed to reflect. In the visible and near infrared range, the average thickness of each layer pair is not more than 0.5 microns.
  • the principle of operation of the film is based on interference and birefringence.
  • the resulting film provides an efficient mirror surface which is substantially non-absorptive and non-transmissiveof light. Openings in the film must be provided for extraction of light.
  • a flexible sheet for a light pipe includes a substrate covered with a plurality of interface layers with differing respective indices of refraction, thereby providing Fresnel reflection, where each layer is thicker than a wavelength of light in the visible region.
  • each layer is at least 1 micron thick.
  • each layer is at least 2 to 10 microns thick.
  • a light pipe includes a multi-layer sheet with differing indices of refraction among adjacent interface layers providing Fresnel reflection, the multi-layer sheet being formed into a conduit, and an extractor arranged lengthwise along the conduit for directing most of the light which encounters the extractor out of the light pipe.
  • Fig. 1 is a schematic, longitudinal cross sectional view of a light pipe which utilizes several concentric sheets of plastic.
  • Fig. 2 is a cross sectional view taken along line 2-2 in Fig. 1.
  • Fig. 3 is a schematic diagram of a multi-layer plastic sheet in accordance with the present invention.
  • Fig. 4 is a graph of reflection versus angle of incidence for several interfacing surfaces with different ratios of indices of refraction.
  • Fig. 5 is a graph of total single net reflection versus angle of incidence for various numbers of sheets or layers.
  • Fig. 6 is a schematic, longitudinal cross sectional view of a light pipe in accordance with the present invention, utilizing the multi-layer plastic sheet of the present invention.
  • Fig. 7 is a cross sectional view taken along line 7-7 in Fig. 6.
  • Fig. 8 is a schematic view of an example light pipe system in accordance with the present invention.
  • Fig. 9 is a schematic view of another example of a light pipe system in accordance with the present invention.
  • Fig. 10 is a schematic view of a light pipe which utilizes several sections of the multi-layer plastic film in accordance with the present invention.
  • Fig. 11 is a schematic view of a tapered, diffuse light extraction used in a light pipe system in accordance with the present invention.
  • a light pipe 3 includes a plurality of concentric plastic sheets 5 separated by an air gap 7.
  • a light source 9 directs light into one end of the pipe 3. Narrow angle light is transported down by the pipe by the Fresnel reflection which occurs at the plastic / air interface. Higher angle light exits the pipe either directly or after encountering an extractor 11. Multiple sheets 5 are utilized to increase the angle of light which can be efficiently transported down the pipe.
  • a narrow angle light source 9 e.g. between about 7° and 14° half angle
  • the present invention provides efficient distribution of light with grazing angle reflection and also with higher angle reflection.
  • the present invention provides such light distribution with a single coated sheet of plastic, thereby simplifying the light pipe construction and reducing material and labor cost.
  • the present invention provides a single plastic sheet substrate covered with one or more layers of plastic with differing indices of refraction.
  • a substrate 17 e.g. a plastic sheet
  • several interface layers L ⁇ through L n of material e.g. coatings, laminates, adhesives, etc.
  • has an index of refraction Ri which is different from the index of refraction of any adjacent interface layer:
  • each interface layer corresponds to one layer of material.
  • each interface layer itself may include several layers of the same material or different materials with the same index of refraction.
  • the interface layers are bonded to each other, but may alternatively simply comprise alternating sheets of plastic with differing indices of refraction. As a practical matter (e.g. simplification of manufacturing) it may be preferred to use only two materials (other than the substrate) with different indices of refraction for the interface layers.
  • the layers of the present invention are preferably thicker than a wavelength of light in the visible region (e.g. at least 1 or 2 microns), while remaining relatively very thin as compared to the plastic sheet substrate. For example twenty 10 micron layers is 200 microns thick or about 0.2 mm.
  • a wavelength of light in the visible region e.g. at least 1 or 2 microns
  • twenty 10 micron layers is 200 microns thick or about 0.2 mm.
  • the layers may be applied by a UV curing process, as a laminate, or as plastic sheets bonded to each other by thermal bonding or ultrasonic bonding.
  • the multi-layer plastic sheet of the present invention is substantially light transmissive for higher angles of incidence (e.g. above 30° from horizontal). The amount of light transmitted varies with the angle of incidence such that grazing angle light is substantially all reflected and light above some other selected angle of incidence is substantially all transmitted (i.e. escapes the light pipe).
  • the angle of incidence for light which is transmitted may be selected, for example, depending on the beam angle of the light source and / or the length of the pipe.
  • An example range of high reflectivity for the present invention is between about 0° from horizontal (grazing) to about 15° or 20° from horizontal (14° being presently preferred), with the reflectivity falling off rapidly above those angles.
  • An example process for making a multi-layer plastic sheet in accordance with the present invention includes applying a thin layer of UV curable plastic of one optical index on a substrate, curing it, and then applying a thin layer of another UV curable plastic with a different index of refraction on top of the previously applied layer and curing it.
  • a large number of layers may be applied while maintaining a sufficiently flexible plastic sheet. For example, starting with a plastic sheet, apply a thin layer of a first UV curable coating (e.g. spray, dip, or squeegee) to the sheet. Expose the coated plastic to UV light to cure the coating. Next, apply a thin layer of a second UV curable coating to the plastic sheet in similar manner and cure with UV light. Repeat as necessary for the desired number of layers.
  • the first and second coatings have different indices of refraction and also low absorption.
  • Another example process according to the invention is as follows. Start with a base sheet of polycarbonate about 10 mils thick. Apply a thin layer of an optically transparent adhesive which has a different index of refraction after drying. For example, the adhesive is squeezed out of a tube and spread evenly with a squeegee. Put down a thin (e.g. 1 mil) sheet of polycarbonate. The glue is transparent with a different index of refraction from the plastic, thus providing the desired optical interface. This process can be performed by hand or may be automated to apply many layers. The resulting multi-layer plastic sheet is thin, light, and flexible.
  • An example automated process according to the invention is as follows.
  • a roll of plastic sheeting is fed through various processing stations by rollers.
  • the next station is a UV light which cures the coating.
  • Another subsequent station sprays on a UV curable coating with a different index of refraction which is cured by another downstream UV light station.
  • Many such pairs of stations may be alternated to provide the desired number of layers.
  • the sheet may loop through or pass back and forth through the same stations multiple times to provide the desired number of layers. The result is a low cost manufacturing arrangement for the multi-layer plastic sheet.
  • Fig. 4 is a graph of approximated reflection versus angle for various indices of refraction for two materials providing a single interface. Each line represents the reflection of a single interface.
  • the amount of Fresnel reflection for a given angle of incidence is a function of a ratio of the indices of refraction of the two materials providing the interface.
  • Both polarities (TM and TE) are graphed for the ratio of 1.6. Only the TM polarity is graphed for the ratios of 1.1 and 1.2 (the TE polarity provides higher reflection).
  • Indices of refraction for different commercially available plastic materials are given below in Table 1.
  • Various acrylic materials are commercially available which can be UV cured with a refractive index in the range of 1.5 to 1.6.
  • Loctite of Rocky Hills, CT sells LoctiteTM 3100 with a nominal cured refractive index of 1.51.
  • Another Loctite product, SuperBonderTM 498 has a nominal cured refractive index of 1.45.
  • Raymat, Inc. of Tinley Park, IL sells a variety of low refractive index claddings under the name OPTI-CLAD which have indices of refraction in the range of 1.36 to 1.49.
  • Rad-Cure Corporation of Fairfield, NJ provides a UV curable high gloss hard coat for plastics under the name RAD-KOTE 503SP.
  • the index of refraction is in the range of 1.43 to 1.54.
  • a desired ratio n1/n0 may be provided in the range of 1.1 to 1.2.
  • the foregoing are only examples and a wide variety of other materials with a wide range of indices of refraction are available and suitable for use in accordance with the present invention.
  • a large differential between the two indices is preferred and it is also preferred that the lower index be as low as possible.
  • Higher ratios generally provide higher reflectivity and require fewer layers to provide a desired amount of reflection as compared to a lower ratio.
  • Increasing the number of layers generally increases the amount of reflection at angles of incidence near normal (i.e. 90° from horizontal), although relatively high reflection at normal (e.g. up to about 30%) does not detract significantly from the operation of the light pipe. Using as few layers as necessary (e.g.
  • a light pipe e.g. a 30 feet long, 6 inch diameter pipe
  • 85%-90% total net reflection provides good performance in a light pipe.
  • a light pipe 21 includes a multi-layer plastic sheet 23 having the structure described in connection with Fig. 3 above.
  • An outer shell or carrier 25 support the sheet 23. No air gap is necessary between the sheet 23 and the carrier 25.
  • An extractor 27 is arranged along the length of the pipe to direct light out of the light pipe 21.
  • a light source 29 provides a beam of light into the light pipe 21.
  • the carrier 25 may have a diffuse interior and / or exterior surface for diffusing light which exits the pipe 21.
  • the extractor 27 preferably has an opaque diffuse reflecting surface adjacent to the sheet 23 so that light which is not reflected down the pipe 21 by the sheet 23 is scattered into mostly high angle light which exits the pipe 21 near the point where the light encountered the extractor 27.
  • a light pipe 30 includes a multi-layer plastic sheet 31 suspended by a mounting bracket 33. Respective edges of the sheet 31 are inserted in and secured to slots 35a and 35b of the bracket 33.
  • the light pipe 30 omits the carrier 25.
  • An extractor 37 is disposed on an outside surface of the sheet 31.
  • An optional strip 39 covers a surface of the bracket 33 which is interior to the light pipe 30.
  • the strip 39 may be specular or diffuse, or may exhibit a combination of specular and diffuse properties such as the white vinyl tape discussed in the '815 publication.
  • a light pipe 40 is similar to the light pipe 30, including a multi-layer plastic sheet 41 , except that the extractor 47 is disposed on an inside surface of the sheet 41.
  • the extractor 47 may be specular or diffuse, or may exhibit a combination of specular and diffuse properties such as the white vinyl tape discussed in the '815 publication.
  • the optional strip 49 exhibits similar optical properties as compared to the extractor 47.
  • a light pipe 50 in accordance with the present invention includes a plurality of section 51 , 53, 55 of multi-layer plastic sheet material.
  • a light source 57 directs light into the pipe 50.
  • at least one of sections 51 , 53, and 55 provides a different number of layers as compared to one of the other sections.
  • section 51 may have 40 layers, while section 53 has 20 layers and section 55 has ten layers.
  • the light pipe 50 may be made from a single sheet of plastic which is processed differently in the different sections 51 , 53, and 55 to provide the different number of layers.
  • the sections 51 , 53, and 55 may be separate sheets of multi-layer plastic with seams or couplings therebetween.
  • different numbers of sections and different number of layers may be utilized to adjust the light output for a given installation.
  • a light pipe 60 (including a multi-layer plastic sheet) includes an extractor 61 which is tapered along its length with a narrow end of the taper near a light source 63 and a relatively wider end of the taper distal to the light source 63. Adjusting the shape of the extractor affects how much light is scattered out of the light pipe at any given point along the length of the light pipe. Other shapes and configurations for the extractor may be utilized as necessary to provide a more uniform light output.

Abstract

L'invention concerne une feuille flexible (23) pour conducteur de lumière (21), qui présente un substrat recouvert d'une pluralité de couches d'interface à différents indices de réfraction respectifs, assurant ainsi une réflexion de Fresnel; chaque couche est plus épaisse qu'une longueur d'onde de lumière dans la partie visible du spectre. Par exemple, chaque couche a une épaisseur d'au moins un micron. De préférence, chaque couche a une épaisseur comprise entre au moins 2 et 10 microns. L'invention concerne en outre un conducteur de lumière (21) qui comprend un conduit réalisé à partir de la feuille (23) considérée, et un extracteur (27) disposé dans le sens de la longueur du conduit permet de diriger hors du conducteur de lumière (21) la plupart de la lumière qui frappe cet extracteur (27).
PCT/US2001/016523 2000-07-24 2001-07-11 Feuille en plastique multicouche pour conducteur de lumiere WO2002008808A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US22016000P 2000-07-24 2000-07-24
US60/220,160 2000-07-24

Publications (1)

Publication Number Publication Date
WO2002008808A1 true WO2002008808A1 (fr) 2002-01-31

Family

ID=22822311

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2001/016523 WO2002008808A1 (fr) 2000-07-24 2001-07-11 Feuille en plastique multicouche pour conducteur de lumiere

Country Status (1)

Country Link
WO (1) WO2002008808A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5661839A (en) * 1996-03-22 1997-08-26 The University Of British Columbia Light guide employing multilayer optical film
US5882774A (en) * 1993-12-21 1999-03-16 Minnesota Mining And Manufacturing Company Optical film
US6297906B1 (en) * 1996-02-29 2001-10-02 3M Innovative Properties Company Light fixture containing optical film

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5882774A (en) * 1993-12-21 1999-03-16 Minnesota Mining And Manufacturing Company Optical film
US6297906B1 (en) * 1996-02-29 2001-10-02 3M Innovative Properties Company Light fixture containing optical film
US5661839A (en) * 1996-03-22 1997-08-26 The University Of British Columbia Light guide employing multilayer optical film

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