WO2009045750A1 - Stratifié de guide de lumière pour réduire la perte de réflecteur - Google Patents

Stratifié de guide de lumière pour réduire la perte de réflecteur Download PDF

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Publication number
WO2009045750A1
WO2009045750A1 PCT/US2008/076946 US2008076946W WO2009045750A1 WO 2009045750 A1 WO2009045750 A1 WO 2009045750A1 US 2008076946 W US2008076946 W US 2008076946W WO 2009045750 A1 WO2009045750 A1 WO 2009045750A1
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WIPO (PCT)
Prior art keywords
lightguide
optically thick
light
reflector
interference reflector
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Application number
PCT/US2008/076946
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English (en)
Inventor
Brian A. Kinder
Jie Zhou
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3M Innovative Properties Company
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Publication of WO2009045750A1 publication Critical patent/WO2009045750A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0055—Reflecting element, sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0051—Diffusing sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0053—Prismatic sheet or layer; Brightness enhancement element, sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side

Definitions

  • This invention generally relates to lightguides and displays incorporating same.
  • the invention relates to lamination of reflectors to lightguides.
  • Optical displays such as liquid crystal displays (LCDs)
  • LCDs are becoming increasingly commonplace, finding use for example in mobile telephones, portable computer devices ranging from hand held personal digital assistants (PDAs) to laptop computers, portable digital music players, LCD desktop computer monitors, and LCD televisions.
  • PDAs personal digital assistants
  • LCDs are becoming thinner as the manufacturers of electronic devices incorporating LCDs strive for smaller package sizes.
  • the backlight typically includes a lightguide in the form of a slab or wedge, often made of an optically transparent polymeric material produced by, for example, injection molding.
  • the backlight includes one or more light sources that couple light into the lightguide from one or more edges of the lightguide.
  • the coupled light typically travels through the lightguide by total internal reflection from the top and bottom surfaces of the lightguide until encountering some feature that causes a portion of the light to exit the lightguide.
  • Many backlights include a reflector that is used to more efficiently utilize light that may exit the bottom surface of the lightguide.
  • a lightguide laminate includes an optically thick lightguide, an optically thick adhesive layer, and an interference reflector.
  • the optically thick lightguide has a refractive index n g over a wavelength range of interest
  • the optically thick adhesive has a refractive index n a dh over the wavelength range of interest.
  • the refractive index of the optically thick adhesive is less than the refractive index of the optically thick lightguide over the wavelength range of interest.
  • the optically thick lightguide has first and second major surfaces, and the optically thick adhesive layer is in contact with the second major surface of the optically thick lightguide.
  • a backlight assembly includes a light source for injecting light into an edge of a lightguide laminate, and also includes a light recycling stack.
  • the lightguide laminate further includes an optically thick lightguide, an optically thick adhesive layer, and an interference reflector.
  • the optically thick lightguide has a refractive index n g over a wavelength range of interest
  • the optically thick adhesive has a refractive index n a dh over the wavelength range of interest.
  • the refractive index of the optically thick adhesive is less than the refractive index of the optically thick lightguide over the wavelength range of interest.
  • the optically thick lightguide has first and second major surfaces, and the optically thick adhesive layer is in contact with the second major surface of the optically thick lightguide.
  • the interference reflector is also in contact with the adhesive layer, opposite the optically thick lightguide.
  • the interference reflector substantially reflects light over the wavelength range of interest.
  • the light recycling stack is positioned proximate the first major surface of the lightguide.
  • a liquid crystal display in another aspect of the invention, includes a liquid crystal display module and a backlight assembly.
  • the backlight assembly includes a light source for injecting light into an edge of a lightguide laminate, and also includes a light recycling stack.
  • the lightguide laminate includes an optically thick lightguide, an optically thick adhesive layer, and an interference reflector.
  • the optically thick lightguide has a refractive index n g over a wavelength range of interest
  • the optically thick adhesive has a refractive index n a dh over the wavelength range of interest.
  • the refractive index of the optically thick adhesive is less than the refractive index of the optically thick lightguide over the wavelength range of interest.
  • the optically thick lightguide has first and second major surfaces, and the optically thick adhesive layer is in contact with the second major surface of the optically thick lightguide.
  • the interference reflector is also in contact with the adhesive layer, opposite the optically thick lightguide.
  • the interference reflector substantially reflects light over the wavelength range of interest.
  • the light recycling stack is positioned proximate the first major surface of the lightguide.
  • FIG. 1 is a schematic cross-sectional view of a backlit display
  • FIG. 2 is a schematic showing the path of light rays in a lightguide assembly
  • FIG. 3 is a plot showing spectral transmission for a lightguide
  • FIG. 4 is a plot showing spectral transmission for another lightguide.
  • a thin film interference stack for that purpose.
  • Such stacks can be made economically, and can be designed to provide high reflectivity over a desired wavelength band, such as the human visible wavelength spectrum or the output spectrum of a specified light source or the sensitivity spectrum of a specified detector.
  • the stacks can also provide reflectivity over a range of angles of the incident light. Excellent reflectivity can usually be achieved — at a particular wavelength, or even over the entire wavelength range of interest — for normally incident light and for moderate angles of incidence. This performance is usually adequate for the intended end-use application.
  • Examples of interference reflectors, such as multilayer interference reflectors include those described in U.S. Pat. Nos.
  • a birefringent multilayer stack adapted to reflect visible light can be used to reflect and distribute some of the light that is injected into the edge of a lightguide.
  • a birefringent multilayer stack is a multilayer interference reflector available from 3M Company under the trade designation Vikuiti ESRTM (Enhanced Specular Reflective) film.
  • Acceptable performance of such backlights is achieved by suspending the ESR film below the lightguide such that the ESR film is immersed in a very low refractive index medium such as air, for optimal performance.
  • a very low refractive index medium such as air
  • optical losses can arise if the ESR film ceases to be immersed in the low refractive index medium, for example, if the ESR film comes in contact with the lightguide or another portion of the display, on both sides of the ESR film simultaneously.
  • the present description discloses a technique to reduce optical losses from a reflector in a display, for example, a hand-held display device.
  • the optical losses are reduced by laminating the reflector to the lightguide with an optical adhesive.
  • the lightguide and reflector are prevented from inadvertent contact, which can cause undesired light transmission through the reflector (light leakage) in the region of contact.
  • Selection of an optical adhesive with an appropriate refractive index can reduce or eliminate this undesired light transmission through the reflector, such as an interference reflector.
  • optically thick materials refer to a material thickness that is generally greater than the wavelength of light, preferably orders of magnitude greater, for example at least 1 micrometer, and possibly hundreds of micrometers or more.
  • Geometrical optics can sufficiently predict or describe optical properties of an optically thick film, such as its reflective and transmissive properties.
  • interference optics can be used to sufficiently describe the behavior of light traveling in interference films, such as the thin film layers in multilayer interference reflectors.
  • Interference reflectors such as multilayer interference reflectors, can be made from inorganic materials, such as alternating layers of metals or oxides, and can be electrically conductive or non-conductive reflectors. In some cases, multilayer interference reflectors can be made from organic materials.
  • a polymeric multilayer interference reflector such as an ESR film can be laminated to an optically thick substrate such as a lightguide, using an optically thick adhesive with a refractive index lower than the optically thick substrate.
  • Light that is injected into the edge of the optically thick substrate of such a laminated lightguide is guided along the lightguide by total internal reflection (TIR), and undesired light leakage through the ESR film is minimized.
  • TIR total internal reflection
  • the light guided along the lightguide can be extracted where desired, for example by interaction with extraction features as described elsewhere in this description.
  • a multilayer interference reflector such as an ESR film can leak light incident to its surface, depending on the medium that the film is immersed in.
  • a "leak angle" can be reached.
  • the leak angle is the angle such that most of the light incident on the multilayer interference reflector surface, at or greater than the leak angle, is transmitted through the film. At angles of incidence less than the leak angle, most of the light is reflected from the multilayer interference reflector surface.
  • the leak angle can be dependent on the materials and layer thicknesses in the multilayer interference reflector, the medium in which the multilayer interference reflector is immersed, and the wavelength of the incident light. The leak angle is significantly reduced (i.e.
  • the multilayer interference reflector leaks more incident light) when the refractive index surrounding the multilayer interference reflector is increased.
  • the leak angle of the reflector can be influenced by each of the different materials; however, if one of the materials is air, light propagating within the multilayer interference reflector and incident to the surface that is immersed in air, undergoes reflection from a surface that has a high relative leak angle. Reduction in the leak angle of a multilayer interference reflector (by immersion in a higher index material), can adversely affect the brightness and uniformity of a display.
  • F-TIR frustrated total internal reflection
  • the lightguide and ESR film reflector are separated in the display backlight by an air gap, and a spacer surrounding the lightguide can be used to maintain the air gap.
  • the spacer may not always protect the air gap, and debris may enter the space between lightguide and reflector. This debris can cause optical coupling and light leakage, resulting in display dark spots and increased non-uniformity.
  • the lightguide and reflector can move independently of each other, and can distort or warp. Warping caused by, for example thermal changes, can cause the reflector and lightguide to contact each other, resulting in light leakage. In some cases, changes in humidity and static electricity can also cause optical coupling and light leakage.
  • the present invention laminates an interference reflector such as an ESR film to the optically thick lightguide using an optically thick adhesive having an index of refraction (n a dh) less than the refractive index of the lightguide (n g ).
  • the refractive index difference can be chosen such that substantially all injected light remains in the lightguide, and does not enter the ESR film at angles greater than the leak angle.
  • the n a dh can also be chosen such that light recycled back (e.g.
  • DBEF VikuitiTM Dual Brightness Enhancement Film
  • the lightguide can be of any desired size or shape, and can be of uniform thickness such as a slab, or tapered such as a wedge.
  • the lightguide can, for example, be suitable for use in a backlight for a liquid crystal display (LCD) in a mobile phone, laptop computer, television, or other application.
  • Extraction features can be provided on a front surface or elsewhere on or in the lightguide, to direct light out of the lightguide towards a liquid crystal panel or other component to be illuminated.
  • the lightguide can include extraction features on the side opposite of the laminated reflector, causing light to be directed toward the viewer at predetermined angles. Examples of extraction features can be found, for example, in U.S. Patents 6,845,212
  • the extraction features can be grooves, lenslets, or other microstructured features designed to extract light from the lightguide.
  • the extraction features can be imparted to the lightguide using several methods, including but not limited to: casting, embossing, microreplicating, printing, ablating, etching and other methods known in the art.
  • the present invention also provides a lightguide and a reflector as a single unit, such as a lightguide laminate, reducing the backlight part count and cost to a backlight assembler.
  • Lamination of the lightguide to the reflector prevents debris from entering between the two surfaces, causing defects in display uniformity.
  • Appropriate selection of lightguide and adhesive refractive indices can preserve lightguiding and prevent light from entering the reflector at an angle greater than the leak angle.
  • the lamination of the two components may also reduce warp of the individual components, resulting in improved environmental performance and stability.
  • a wavelength range of interest can mean visible or near-visible light (e.g., 400-700 nm wavelength), near infrared light (e.g., 700- 1000 nm, 700-1400 nm or 700-5000 nm with the selection of one of these ranges sometimes being dependent on the detector or transmission medium employed), or both visible and near infrared light, or portions thereof.
  • Other ranges may also be used as the wavelength range of interest.
  • the wavelength range of interest may be relatively narrow (e.g., 100 nm, 50 nm, 10 nm, or less).
  • the wavelength range of interest may be broader (e.g., 400-800 nm, 400-900 nm, 400-1000 nm, 400-1200 nm, 400-1400 nm, 400-1600 nm or 400-1700 nm).
  • the multilayer interference reflector stack includes typically tens, hundreds, or thousands of microlayers, composed of optical materials "a" and "b" arranged in an interference stack, for example a quarter-wave stack.
  • Optical materials "a, b” can be any suitable materials known to have utility in interference stacks, whether inorganic (such as Ti ⁇ 2, Si ⁇ 2, CaF, or other suitable materials) or organic, e.g., polymeric (e.g. polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), acrylic, and other suitable materials).
  • the stack may have an all-inorganic, all-organic, or mixed inorganic/organic construction.
  • the stack can include more materials than just materials "a,b", for example, additional materials "c", "d”, and the like can be included in the stack.
  • the microlayers can be isotropic, or they can be birefringent microlayers, or they can be a combination of isotropic microlayers and birefringent microlayers.
  • Birefringent microlayers may be utilized in symmetric reflective systems, which reflect normally incident light of any polarization substantially equally, or in asymmetric reflective systems, which have high reflectivity for normally incident light of one polarization and lower reflectivity for normally incident light of an orthogonal polarization.
  • a microlayer has an optical thickness (physical thickness multiplied by refractive index) that is typically a fraction of a wavelength of light.
  • the microlayers are arranged in repeating patterns, referred to as optical repeat units (ORUs), for example where the optical thickness of the ORU is half the wavelength of light in the wavelength range of interest.
  • ORUs optical repeat units
  • Such thin layers make possible the constructive or destructive interference of light responsible for the wavelength-dependent reflection and transmission properties of the stack.
  • the ORU can be the pair of layers "ab", but other arrangements are also possible, such as the arrangements discussed in U.S. Patent Nos. 5,103,337 (Schrenk et al), 3,247,392 (Thelen), 5,360,659 (Arends et al), and 7,019,905 (Weber).
  • a thickness gradient wherein the optical thickness of the ORUs changes along a thickness dimension of the stack, can be incorporated into the stack to widen the reflection band, if desired.
  • the stack need not be flat or planar over its entire extent, but can be shaped, molded, or embossed into non-planar shapes as desired. At least locally, however, the microlayers can be said to lie or extend substantially parallel to a local x-y coordinate plane.
  • alternating materials of suitable refractive index, microlayer thickness profile across the stack, and total number of microlayers can be selected to provide a stack having characteristics such as: a reflection band extending throughout the visible region and extending into the near infrared, having sharp left- and right-band edges, and having a high average reflectivity throughout at least the visible region (and for some applications also throughout the near infrared) of at least 70%, 80%, or 90% or more.
  • a reflection band extending throughout the visible region and extending into the near infrared, having sharp left- and right-band edges, and having a high average reflectivity throughout at least the visible region (and for some applications also throughout the near infrared) of at least 70%, 80%, or 90% or more.
  • ESR VikuitiTM Enhanced Specular Reflector
  • the film stack can be entirely polymeric, and can be made by a coextrusion process and a stretching process to induce an appropriate amount of birefringence in the microlayers to enhance reflectivity.
  • the film stack can include or be limited to inorganic materials, and may be made by vacuum evaporation techniques.
  • U.S. Patent 6,590,707 Weber for a birefringent thin film stack that utilizes inorganic materials.
  • Backlit display 200 includes a backlight assembly 250, and an LCD module 260.
  • Backlight assembly 250 includes a backlight 220 and an optional light recycling film stack 240 disposed between backlight 220 and LCD module 260.
  • Backlight 220 includes a lightguide laminate 210 and a light source 218.
  • Lightguide laminate 210 includes a reflector 216 adhered to an optically thick lightguide 212 with an optically thick adhesive 214.
  • Light source 218 is positioned to inject light into an edge 211 of optically thick lightguide 212.
  • Light source 218 can be any light source, including for example, a cold cathode fluorescent lamp (CCFL) and a light emitting diode (LED). In some cases, LED light sources are preferred light sources.
  • Reflector 216 can be any reflector having a high reflectivity, for example 90% or greater, for visible light.
  • metalized reflectors and interference reflectors such as multilayer interference reflectors can be used.
  • polymeric multilayer interference reflectors such as an ESR film can be used.
  • Optically thick lightguide 212 can be made from a glass or a polymeric material, such as a thermoplastic or thermoset polymer.
  • a thermoplastic suitable for optically thick lightguide 212 is polycarbonate, but any suitable optically transmissive thermoplastic polymer can be used.
  • Optically thick lightguide 212 can be a homopolymer, copolymer, or a polymer blend.
  • the refractive index of a polymer blend is often referred to as an "effective refractive index" which can be determined experimentally.
  • the refractive index of optically thick lightguide 212 is the refractive index measured at a surface of the lightguide.
  • thermoset materials such as radiation curable acrylates or methacrylates and the like can be used for optically thick lightguide 212.
  • Optically thick lightguide 212 can be a flexible lightguide or a rigid lightguide. Flexible lightguides are described, for example, in U.S. Patent Application Ser. No. 11/421,241.
  • Optional light recycling film stack 240 serves to further condition the light entering LCD module 260 and make more efficient use of the light to improve the brightness and uniformity of backlit display 200.
  • Extracted light 230 leaves backlight 220 from a front surface 222, and enters optional light recycling film stack 240.
  • Light recycling film stack 240 can include a pair of crossed BEF prism films 244 oriented with the prisms facing
  • Light recycling film stack can further include an optional diffuser 242 and an optional DBEF reflective polarizer 246 positioned on opposite sides of crossed BEF prism film 244 as shown.
  • Optional diffuser 242 can be positioned between crossed BEF prism films 244 and backlight 220.
  • optional light recycling film stack 240 can additionally include other films for further conditioning the light, such as diffusers, filters, and the like.
  • a portion of extracted light 230 entering light recycling film stack 240 passes through the stack toward LCD module 260.
  • Another portion of extracted light 230 entering light recycling film stack 240 is directed back into backlight 220 through front surface 222 as recycled light 235. Recycled light 235 enters front surface 222 of lightguide laminate 210 and propagates through optically thick lightguide
  • Recycled light 235 is eventually reflected from reflector 216 and directed back toward front surface 222.
  • Lightguide laminate 210 can be assembled using several different types of optically thick adhesive 214, for example, a dry-film hot melt adhesive, a dry-film pressure sensitive adhesive, a radiation curable adhesive, or a solvent based adhesive.
  • the index of refraction of optically thick adhesive 214 is less than the index of refraction of optically thick lightguide 212. In some cases, the difference between the indices is greater than 0.005, for example greater than 0.01, 0.1, 0.2 or more.
  • the adhesive can form a continuous or a discontinuous layer between optically thick lightguide 212 and reflector 216.
  • a continuous layer of optically thick adhesive 214 can provide uniformity to the display appearance, and improve performance of the backlight.
  • continuous layer means that the layer covers substantially the entire space between optically thick lightguide 212 and reflector 216
  • discontinuous layer means that at least some portion of the space between optically thick lightguide 212 and reflector 216 is not covered by the layer.
  • optically thick adhesive 214 can be made discontinuous, for example by depositing a segmented adhesive pattern on optically thick lightguide 212 or reflector 216.
  • a uniformly discontinuous adhesive pattern can be used, such as a plurality of adhesive segments uniformly distributed over the lightguide.
  • the discontinuous coating is discontinuous on a small scale relative to the dimensions of the lightguide, so that artifacts of the adhesive pattern are not visible when the lightguide is being used.
  • FIG. 2 shows a path of light that is guided within lightguide laminate 210.
  • Light source 218 launches light at a plurality of angles to edge 211 of optically thick lightguide 212 as shown by Lo in FIG. 2.
  • Light rays Lo that are injected into optically thick lightguide 212 begin to propagate within optically thick lightguide 212 at angles less than the critical angle, ⁇ cg , of the normal to edge 211.
  • ⁇ cg critical angle
  • optically thick lightguide 212 undergo TIR at front surface 222, and continue to propagate within optically thick lightguide 212 at angles less than the critical angle, ⁇ cg , of the normal to edge 211.
  • some of light rays L are reflected back into optically thick lightguide 212 by TIR.
  • Some of light rays L, such as rays h, are refracted into optically thick adhesive 214.
  • Light rays h intercept interface 213 at angles greater than ⁇ cga and therefore, are reflected back into optically thick lightguide 212.
  • Light rays h intercept interface 213 at angles less than ⁇ cga and therefore, are refracted into optically thick adhesive 214.
  • front surface 222 is an air interface
  • light rays h propagate within optically thick lightguide 212 at angles greater than the critical angle for both interfaces, and, therefore, undergo TIR within optically thick lightguide 212.
  • light incident at an interface encounters a light extraction feature at or near the interface (not shown in FIG. 2), causing at least a portion of the light to exit the lightguide as extracted light 230 shown in FIG. 1.
  • a light extraction feature at or near the interface (not shown in FIG. 2), causing at least a portion of the light to exit the lightguide as extracted light 230 shown in FIG. 1.
  • Features that can be useful for extracting light can be any of the extraction features disclosed elsewhere in the specification.
  • the extraction features can, for example, be located on front surface 222, on interface 213, internal to optically thick lightguide 212, or a combination thereof.
  • the light rays can reflect several hundreds of times within optically thick lightguide 212.
  • the portion of the light L injected into the lightguide that is refracted into optically thick adhesive 214 on the first interception (I 2 ) can be a small fraction of the total light propagating within the lightguide.
  • Light rays I 2 can be reflected by reflector 216 if the relative index of each layer follows the general relationship: (index of optically thick lightguide 212) > (lowest index within reflector 216) > (index of optically thick adhesive 214). In cases where the inequality is not satisfied, a portion of light rays I 2 can be transmitted through reflector
  • Recycled light 235 enters front surface 222 of optically thick lightguide 212 at a plurality of angles, similar to the manner that light rays L 0 enter edge 211.
  • Front surface 222 of optically thick lightguide 212 also forms an interface with air, and therefore, light rays propagate within optically thick lightguide 212 within the critical angle ⁇ cg of the normal to front surface 222.
  • a portion of recycled light 235 can undergo TIR at interface 213, and another portion can be refracted into optically thick adhesive 214 in the manner described for light rays L, elsewhere. However, since ⁇ cg ⁇ ⁇ cga , a larger portion will be refracted into optically thick adhesive 214 and then reflected by the reflector toward front surface 222.
  • Example 1 Light loss from Polycarbonate lightguide with and without lamination
  • a 20 mil (0.51 mm) thick polycarbonate lightguide film (LEXAN® polycarbonate film 8010, available from GE Polymershapes, Seattle WA) was laminated to a piece of Vikuiti ESRTM film (available from 3M Company) using a ⁇ 3mil (.075 mm) thick optical adhesive (Opt- 1 Laminating adhesive, also known as Bonding Systems Division 9483 adhesive, available from 3M Company).
  • the refractive index of the polycarbonate film was 1.586, and the refractive index of the optical adhesive was 1.47.
  • the lamination was performed using a benchtop laminator (Catena 35, available from General Binding Corporation, Northbrook IL) at room temperature and 1.5 ft/min (0.76 cm/sec).
  • the laminated sample, and an additional sample of bare polycarbonate lightguide film were then cut to a width of about 6 cm and a length of 30 cm for testing.
  • Total light loss (due to leakage, absorption, and scattering) of both the laminated sample and bare films was determined using a light source and an integrating sphere.
  • Laser light at 543 nm was expanded using a beam expander, then flattened by a cylindrical lens, and then focused onto the edge of the film.
  • the light intensity was measured using a photo detector attached to the integrating sphere.
  • the film was then cut back 5 cm, and the process was repeated until only 10 cm of the original 30 cm remained.
  • the total light loss measurement was repeated twice for each of the bare and laminated films. The losses measured in the laminated sample and the bare film were substantially equal, indicating that there was no significant light loss due to the lamination of the ESR film to the polycarbonate. The total light loss experiment described above was then repeated with the exception that an LED light source was used instead of the Laser.
  • the LED light source consisted of four LEDs removed from a Nokia 7270 cellular phone (available from Nokia Group, Finland). The LEDs were aligned side -by-side and separated by a few mm in the device. The LED light source was operated at 13.7V and 20 mA. The total light loss measurement indicated that there was no significant light loss due to the lamination of the ESR film to the polycarbonate.
  • Example 2 Transmission spectra of polycarbonate lightguide with ESR film
  • the transmission spectra of a polycarbonate lightguide with ESR film were measured at different incidence angles using a Lambda 900 spectrophotometer, available from Perkin/Elmer. This Example demonstrated that lamination of ESR film to a polycarbonate lightguide did not cause significant decrease in the reflectivity of ESR film.
  • the light incident to each sample entered the surface of the polycarbonate opposite to the ESR film.
  • the transmission of each sample was measured in the visible region of the spectrum from 400nm - 700nm.
  • the spectra of the laminated sample of Example 1 are shown in FIG. 3 for 0, 15, 30, 45, 60, and 75 degree incidence angles.
  • the spectra of the bare polycarbonate film of Example 1, with ESR film suspended below the bare polycarbonate film i.e.
  • Example 3 Brightness and uniformity of ESR laminated to a polycarbonate lightguide
  • Two 15 mil (381 microns) thick lightguide slabs were constructed out of thick polycarbonate film (Panlite 1151, available from Teijin Kasei, Alpharetta GA). Both lightguides had the same extractors on one surface, to extract light out of a 32 mm x 40 mm area on the lightguide.
  • An ESR film was laminated to one lightguide on the side opposite of the extractors using an optically thick OPT-I adhesive according to the method described in Example 1.
  • Each lightguide was placed in an aluminum housing having a first opening along an edge of the lightguide for receiving light from a light source, and a second opening about 32 mm wide and 40 mm long on the side exposing the extractors.
  • the light source was the 4 edge lit LEDs described in Example 1, operating at 13.7V and 20 mA, aligned to the first opening.
  • the lightguides were held along their edges within the aluminum housing.
  • the second opening in the aluminum frame was covered with three optical films: a diffuser sheet (diffuse polycarbonate, available from GE Polymershapes, Seattle WA) and two crossed prism films (TBEF and BEF-II, both available from 3M Company).
  • the light guide that was not laminated to ESR film had a free floating piece of ESR film suspended below it.
  • a photometric imaging camera (PM- 1600 available from Radiant Imaging Inc.,
  • Duvall WA positioned above the second opening, measured the spatial luminance of the lightguides.
  • the luminance was calibrated with a spot luminance meter (PR-650, available from Photo Research Inc., Chatsworth CA).
  • the brightness and uniformity of these lightguides were compared to each other.
  • the brightness and uniformity of the laminated ESR film lightguide was greater by 23% and 14% respectively, than those of the sample with the free floating ESR film.

Abstract

L'invention porte sur un stratifié de guide de lumière, et sur des dispositifs d'affichage et des rétroéclairages de dispositif d'affichage comprenant de tels stratifiés de guide de lumière. Le stratifié de guide de lumière comprend un guide de lumière optiquement épais, une couche adhésive optiquement épaisse et un réflecteur d'interférence. Le guide de lumière optiquement épais comprend un matériau ayant un indice de réfraction qui est supérieur à l'indice de réfraction de l'adhésif optiquement épais sur une plage de longueur d'onde d'intérêt. Le guide de lumière optiquement épais a des première et seconde surfaces majeures, et la couche adhésive optiquement épaisse est en contact avec la seconde surface majeure du guide de lumière optiquement épais. Le réflecteur est également en contact avec la couche adhésive, à l'opposé du guide de lumière optiquement épais. Le réflecteur est sélectionné pour réfléchir de façon substantielle la lumière sur la plage de longueur d'onde d'intérêt.
PCT/US2008/076946 2007-09-30 2008-09-19 Stratifié de guide de lumière pour réduire la perte de réflecteur WO2009045750A1 (fr)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2513691A1 (fr) * 2009-12-16 2012-10-24 Saint-Gobain Glass France Panneau a diodes electroluminescentes
US8475689B2 (en) 2003-06-30 2013-07-02 Johnson & Johnson Consumer Companies, Inc. Topical composition containing galvanic particulates
US9044397B2 (en) 2009-03-27 2015-06-02 Ethicon, Inc. Medical devices with galvanic particulates
WO2016106144A1 (fr) * 2014-12-23 2016-06-30 3M Innovative Properties Company Stratifié de réflecteur
CN105974664A (zh) * 2016-06-21 2016-09-28 青岛海信电器股份有限公司 背光模组、显示装置及背光模组的制作方法

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JPH08262438A (ja) * 1995-03-23 1996-10-11 Alps Electric Co Ltd 液晶表示装置のバックライト構造
JP2003202568A (ja) * 2001-10-24 2003-07-18 Sharp Corp 導光体およびその製造方法、面状光源装置、表示装置
JP2003263913A (ja) * 2002-03-11 2003-09-19 Minebea Co Ltd 面状照明装置
US6659615B2 (en) * 2000-01-13 2003-12-09 Nitto Denko Corporation Light pipe and method for producing the same

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Publication number Priority date Publication date Assignee Title
JPH08262438A (ja) * 1995-03-23 1996-10-11 Alps Electric Co Ltd 液晶表示装置のバックライト構造
US6659615B2 (en) * 2000-01-13 2003-12-09 Nitto Denko Corporation Light pipe and method for producing the same
JP2003202568A (ja) * 2001-10-24 2003-07-18 Sharp Corp 導光体およびその製造方法、面状光源装置、表示装置
JP2003263913A (ja) * 2002-03-11 2003-09-19 Minebea Co Ltd 面状照明装置

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8475689B2 (en) 2003-06-30 2013-07-02 Johnson & Johnson Consumer Companies, Inc. Topical composition containing galvanic particulates
US8734421B2 (en) 2003-06-30 2014-05-27 Johnson & Johnson Consumer Companies, Inc. Methods of treating pores on the skin with electricity
US9044397B2 (en) 2009-03-27 2015-06-02 Ethicon, Inc. Medical devices with galvanic particulates
EP2513691A1 (fr) * 2009-12-16 2012-10-24 Saint-Gobain Glass France Panneau a diodes electroluminescentes
WO2016106144A1 (fr) * 2014-12-23 2016-06-30 3M Innovative Properties Company Stratifié de réflecteur
CN107111184A (zh) * 2014-12-23 2017-08-29 3M创新有限公司 反射器层合体
CN105974664A (zh) * 2016-06-21 2016-09-28 青岛海信电器股份有限公司 背光模组、显示装置及背光模组的制作方法

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