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
  • G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
  • G02B6/0023—Means for improving the coupling-in of light from the light source into the light guide provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
  • G02B6/0031—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
  • G02B6/0081—Mechanical or electrical aspects of the light guide and light source in the lighting device peculiar to the adaptation to planar light guides, e.g. concerning packaging
  • G02B6/0086—Positioning aspects
  • G02B6/0088—Positioning aspects of the light guide or other optical sheets in the package
• • 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
  • G02F1/133504—Diffusing, scattering, diffracting elements
• • 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
  • G02F1/133528—Polarisers
  • G02F1/133536—Reflective polarizers
• • 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
  • G02F1/133553—Reflecting elements
• • 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
• • 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
  • G02B6/0066—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 characterised by the light source being coupled to the light guide
  • G02B6/0068—Arrangements of plural sources, e.g. multi-colour light sources

Definitions

• the disclosure generally relates to backlit illumination systems, specifically to a backlight for providing uniform illumination to a display panel.
• LCDs are used in a variety of applications ranging from relatively large devices including computer monitors and televisions, to small, handheld devices such as cell telephones, portable DVD players, wristwatches, gaming devices, and other applications.
• a widely-used type of display is the liquid crystal display (LCD). Because LCDs do not create light themselves, they require a source of illumination - either reflected ambient light, or more commonly, light from a backlight.
• the backlight generally includes an illumination device, which may include light sources such as light emitting diodes or fluorescent lamps, and a number of light management films between the illumination device and the LCD panel. In general, the light management films enhance the operation of a display by promoting more efficient and effective use of light.
• a backlight for providing illumination to a liquid crystal panel includes a reflective polarizer.
• the reflective polarizer For a substantially normally incident light and for at least one visible wavelength in a range extending from about 400 nm to about 800 nm, the reflective polarizer reflects at least 60% of the incident light having a first polarization state and transmits at least 60% of the incident light having an orthogonal second polarization state.
• the backlight further includes an extended light source.
• the extended light source includes a diffuse reflective film assembly and an emission surface disposed between the reflective polarizer and the diffuse reflective film assembly. The extended light source is configured to emit light through the emission surface toward the reflective polarizer.
• the diffuse reflective film assembly includes a specularly reflective film.
• the reflective film specularly reflects at least 80% of the incident light for each of the first and second polarization states.
• the diffuse reflective film assembly further includes an optically diffusive film disposed between the emission surface and the specularly reflective film. The optically diffusive film is bonded to the specularly reflective film at a plurality of discrete spaced apart bonded locations.
• the optically diffuse reflective film assembly includes a specularly reflective film. For a substantially normally incident light and for at least one visible wavelength in a wavelength range extending from about 400 nm to about 800 nm, the reflective film specularly reflects at least 95% of the incident light for each of orthogonal first and second polarization states.
• the optically diffuse reflective film assembly further includes an optically diffusive film bonded to the specularly reflective film.
• the bonding pattern includes a plurality of spaced apart bonding areas with a total bonding area of less than about 20%.
• the optically diffusive film includes a plurality of fibers dispersed in a material. At least 20% of the fibers have an average diameter less than about 5 microns. At least 50% of the fibers have an average diameter greater than about 8 microns.
• display systems including a liquid crystal panel disposed on a backlight.
• FIG. 1 schematically illustrates a display system having a backlight for providing illumination to a display panel according to some embodiments of the disclosure
• FIGS. 2 and 3 schematically illustrate different views of a diffuse reflective film assembly according to some aspects of the disclosure
• FIGS. 4A and 4B schematically illustrate different bonding locations between the optically diffusive film and the specularly reflective film
• FIG. 5 schematically illustrates the optically diffuse film according to some aspects.
• FIG. 6 schematically illustrates a prismatic layer disposed between the reflective polarizer and a light source.
• Display panels such as, for instance, Liquid Crystal Displays (LCD)
• LCD Liquid Crystal Displays
• Backlighting technique is an effective means to provide a wide range of brightness for independent regions of the display and improves the user visual experience.
• One method of backlit illumination utilizes discrete light sources such as LEDs and a lightguide to spread the light uniformly over the area of the display.
• Backlighting methods generally utilize additional optics to achieve the uniformity and brightness specifications.
• LCD size becomes larger and thinner, as desired in many applications, reflective films tend to warp or become distorted due to various reasons. Such warping may create mura defects, which may appear as low contrast, non-uniform brightness regions.
• Embodiments described herein address these and other challenges to enhance luminance and reduce, or eliminate, brightness mura caused by waving or warping of the reflective film.
• a display system (400) includes a liquid crystal panel (410) disposed on a backlight (300), which provides illumination (31) to the liquid crystal panel (410).
• the liquid crystal panel (410) includes a layer of liquid crystals disposed between panel plates.
• the panel plates are often formed of glass, and may include electrode structures and alignment layers on their inner surfaces for controlling the orientation of the liquid crystals in the liquid crystal layer.
• the backlight (300) includes a reflective polarizer (20) and an extended light source (200).
• the extended light source (200) may include a planar light guide with an extended output surface that emits white light. At least some of the light reflected by the reflective polarizer (20) may be depolarized, and subsequently returned to the reflective polarizer (20) in a polarization state that is transmitted through the reflective polarizer (20) to the liquid crystal panel (410). In this manner, the reflective polarizer (20) may be used to increase the fraction of light emitted by the extended light source (200) that reaches the liquid crystal panel (410), and so the image produced by the display system (400) is brighter.
• the reflective polarizer (20) substantially reflects light having one of orthogonal first and second polarization states (e.g., a first polarization state with the electric field along the x-axis) and substantially transmits light having the other of the first and second polarization states (e.g., a second polarization state with the electric field along the y-axis) for at least one visible wavelength in a range.
• the reflective polarizer (20) may be said to substantially reflect light having a first polarization state if at least 60% of incident light having the first polarization state is reflected through the polarizer (20).
• the reflective polarizer (20) may be said to substantially transmit light having an orthogonal second polarization state if at least 60% of incident light having the orthogonal second polarization state is transmitted from the reflective polarizer (20).
• at least 70%, or at least 80%, of incident light having the orthogonal second polarization state is transmitted from the reflective polarizer (20).
• the at least one visible wavelength includes each visible wavelength in a range from about 400 nm to about 800 nm.
• the reflective polarizer (20) used in the optical systems of the present description may be any suitable type of reflective polarizer.
• the reflective polarizer may be a multilayer optical fdm (MOF) that may be substantially uniaxially oriented as described further elsewhere.
• Substantially uniaxially oriented reflective polarizers are available from 3M Company under the trade designation Advanced Polarizing Film 5 or APF.
• Other types of multilayer optical film reflective polarizers e.g., Dual Brightness Enhancement Film or DBEF available from 3M Company
• DBEF Dual Brightness Enhancement Film
• ⁇ polarizers such as, continuous/disperse phase polarizers, wire grid reflective polarizers, or cholesteric reflective polarizers are used.
• Cholesteric polarizers are often provided along with a quarter wave retarding layer on the output side, so that the light transmitted through the cholesteric polarizer is converted to linear polarization.
• MOF and continuous/disperse phase reflective polarizers rely on the difference in refractive index between at least two materials, usually polymeric materials, to selectively reflect light of one polarization state while transmitting light in an orthogonal polarization state.
• MOF reflective polarizers are described in co-owned U.S. Pat. No. 5,882,774 (Jonza et al.), incorporated herein by reference.
• Commercially available examples of MOF reflective polarizers include Vikuiti(TM) DBEF- D200 and DBEF-D440 multilayer reflective polarizers that include diffusive surfaces, and DBEF-Q that includes relatively thick (5 or 10 mil (125 pm or 250 pm)) skin layers of polycarbonate, available from 3M Company, St. Paul, Minn.
• the extended light source includes a diffuse reflective fdm assembly (100) and an emission surface (160).
• the diffuse reflective fdm assembly (100) and the emission surface (160) may be substantially aligned and co-extensive with each other.
• the emission surface (160) is disposed between the reflective polarizer (20) and the diffuse reflective fdm assembly (100).
• the extended light source (200) is configured to emit light (30) through the emission surface (160) toward the reflective polarizer (20).
• the extended light source (200) includes a lightguide (110) for propagating light (30) therein along a length (x-axis) and a width (y-axis) of the lightguide.
• the lightguide (110) includes the emission surface (160) and is disposed between the emission surface (160) and the diffuse reflective fdm assembly (100). At least one light source (120) is disposed proximate an edge surface (111) of the lightguide (110).
• the at least one light source (120) may be any device capable of emitting light such as, e.g., light emitting diodes, fluorescent lights, noble gas lights, incandescent lights, etc. In the illustrated embodiment shown in FIG.
• At least one exemplary lightguide (110) may be described as being a side-emitting lightguide that is configured to receive light from light sources (120) located on either end of the lightguide (110) and redirect, or reflect, the received light (30) along one or more sides of the lightguide (110) along at least a portion of the length of the lightguide (110) (e.g., a plurality of portions of the length, the entire length, etc.).
• the emission surface (160) and the diffuse reflective fdm assembly (100) define an optical cavity (130) therebetween.
• At least one light source (121) may be disposed in the optical cavity (130).
• a plurality of light sources for example, LEDs, may be disposed in the optical cavity (130), say along the length (x-axis) of the cavity (130).
• the diffuse reflective film assembly (100) includes a specularly reflective film (40) and an optically diffusive film (50) bonded to the specularly reflective film (40).
• the specularly reflective film (40) and the optically diffusive film (50) may be substantially aligned and co-extensive with each other.
• a specularly reflective film (40) is a layer for which an incident light ray is reflected such that the reflected angle is substantially equal to the angle of incidence.
• all surfaces have some deformation which results in some scattering of the reflected light ray. For instance, £ 10% of the incident light may be reflected at angles not equal to the incident angle. In many instances, there is less than 1% of the light reflected at angles not equal to the incident angle.
• the reflective film (40) may be said to substantially reflect light if at least 80% of incident light for each of the first and second polarization states is specularly reflected through the reflective film (40).
• the reflective film (40) specularly reflects at least 90%, or at least 95% of the incident light for each of the first and second polarization states.
• the specularly reflective film (40) has an average specular reflectance of greater than about 99% in a visible range extending from about 450 nm to about 650 nm.
• the at least one visible wavelength includes each visible wavelength in a range from about 400 nm to about 800 nm.
• the specularly reflective film or layer may be a multilayer polymeric mirror film that reflects at least about 95% of light incident on the film. In some instances, the multilayer polymeric mirror film may reflect at least about 98 percent of all incident light, regardless of incident angle. In many cases, the multilayer polymeric mirror film may be Vikuiti(TM) ESR, ESR2, ESR-80v2, ESR100, which are available from 3M Company, St. Paul, Minnesota.
• the specularly reflective film (40) may include a plurality of polymeric layers numbering more than about 50, or more than about 70, or more than about 100, in total.
• the optically diffusive film (50) is disposed between the emission surface (160) and the specularly reflective film (40).
• the diffuse reflective film assembly (100) has a total light reflectance greater than about 90% and a specular reflectance of less than about 50%.
• the total light reflectance of the diffuse reflective film assembly (100) may be greater than 95%, or greater than 97% , and a specular reflectance may be less than about or less than 40%, or less than 30% , or less than 20%, or less than 10%, for each of the first and second polarization states.
• the optically diffusive film (50) includes a plurality of fibers (91).
• a ratio of a total weight of the fibers to a total weight of the optically diffusive film may be greater than about 80%, or greater than about 85%, or greater than about 90%.
• the plurality of fibers (91) in the optically diffusive film (50) may be dispersed in a material (92).
• the optically diffusive film (50) may include a non-woven layer (90) having a plurality of fibers (91).
• a ratio of a total weight of the fibers (91) to a total weight of the non- woven layer (90) may be greater than about 50%, or greater than about 70%, or greater than about 90%. In some instances, a ratio of a total weight of the fibers (91) to a total weight of the non-woven layer (90) may be greater than about 95%.
• the plurality of fibers (91) in the non-woven layer (90) may be dispersed in a material (92).
• the non-woven layer (90) may contain core-sheath fiber.
• the core-sheath fiber acts as a thermal bonding agent and the non-woven layer (90) can be heat laminated to the specular reflective film (40) with the core-sheath fiber.
• the content of the core-sheath fiber may be more than 10%.
• the fibers (91) have an average diameter less than about 10 microns, or less than 8 microns in some embodiments.
• the fibers (91) may be a micro fiber having an average diameter of less than or equal to about 3 microns.
• Micro fiber enhances diffuse reflection and increases luminance. Micro fiber also reduces the increase of the value color x, and color y of the display system (400). The content of this micro fiber may be more than 20%. In some embodiments, at least 20% of the fibers (91) have an average diameter less than about 5 microns, and at least 50% of the fibers (91) have an average diameter greater than about 8 microns.
• At least 70% of the fibers (91) have an average diameter of about 3 microns, and at least 30% of the fibers (91) have an average diameter of about 12 microns.
• An optically diffusive layer (170) may be disposed between the extended light source (200) and the reflective polarizer (20), in some aspects, for diffusing light emitted by the extended light source (200). The optically diffusive layer (170) may aid in extracting light, to further condition the output light angle distribution for substantially uniform distribution of light.
• Optically diffusive layer (170) may be any optically diffusive layer that may be desirable and/or available in an application.
• the optically diffusive layer can include a plurality of particles, such as a plurality of Ti02 particles, dispersed in a binder where the particles and the binder have different indices of refraction.
• the optically diffusive layer has an optical haze that is not less than about 40%, or not less than about 50%, or not less than about 60%, or not less than about 70%, or not less than about 80%, or not less than about 90%, or not less than about 95%.
• one or more prismatic layers (140, 150) may be disposed between the reflective polarizer (20) and the emission surface (160).
• the reflective polarizer (20), the emission surface (160) of the extended light source, and the one or more prismatic layers (140, 150) may be substantially co-extensive with each other, in some aspects.
• the one or more prismatic layers (140, 150) include a plurality of prismatic structures (141) as illustrated in FIG. 6.
• one or more prismatic layers (140, 150) may be placed above the optically diffusive layer (170), either unattached or coupled with each other, with the prism structure facing the extended light source (200).
• the optically diffusive layer (170) extracts light from the diffuse reflective film assembly (100), while the prismatic layers (140, 150) redirects the angle distribution, and reimages the output from the diffuse reflective film assembly (100) to improve uniformity.
• Images and conoscopic output that provides maximum brightness and good uniformity may be simulated as a function of an apex angle of the prisms.
• the apex angle may be around 50° - 80° for good uniformity and output angle distributions.
• the optically diffusive film (50) is bonded to the specularly reflective film (40).
• the optically diffusive film (50) may be bonded to the specularly reflective film (40) at a plurality of discrete spaced apart bonded locations (60) as illustrated in FIG. 1, and more clearly shown in FIGS. 2 and 3.
• the plurality of discrete spaced apart bonded locations may form a regular array (61), as schematically shown in FIG. 4A, or may form an irregular array (62).
• the irregular array of the bonded locations includes substantially randomly arranged bonded locations (60) as best seen in FIG. 4B. As best seen in FIG.
• the specularly reflective film (40), the optically diffusive film (50), and the plurality of discrete spaced apart bonded locations (60) define an air-filled space (70) therebetween.
• the specularly reflective fdm (40) may be bonded to the optically diffusive fdm (50) via an adhesive bump (80) at at least one of the bonded locations (60).
• acrylic microsphere adhesive (MSA) may be used for the bonding of optically diffusive fdm (50) with the specular reflective fdm (40).
• MSA is usually prepared by conventional suspension polymerization with a monomer composition. Contact area ratio can be controlled by the average size of MSA and coating volume.
• the bonding locations (60) form a bonding pattern of a plurality of spaced apart bonding areas (Ab).
• the bonding pattern in some embodiments may be a regular pattern, and in other embodiments may be an irregular pattern.
• Each bonding location (60) defines a bonded area (Ab) of a major surface (41) of the specularly reflective fdm (40).
• a ratio of a total bonding area to a total area of the major surface (41) may be less than about 20%, or less than 10% in other embodiments.
• non-woven fibers (91) a combination of Tepyrus TA04PN (manufactured by Teijin), having a diameter of about 3 microns, and Tepyrus TJ04CN (manufactured by Teijin), having a diameter of 12 microns were mixed together as fiber ingredient.
• Tepyrus TA04PN manufactured by Teijin
• Tepyrus TJ04CN manufactured by Teijin
• 70wt% Tepyrus TA04PN and 30wt% of Tepyrus TJ04CN may be used as fiber ingredient.
• Fiber setting and calendering process may be used for making non-woven optically diffusive fdm (50) having a thickness of about 34 micron with a total transmittance of about 64%.
• Acrylic MSA coating solution having a formulation including MSA suspension, de-ionized water, isopropyl alcohol, 1,3-dioxolane in appropriate ratios was prepared. Each ingredient was input into an ampoule bottle and mixed before coating. Coating of Acrylic MSA solution
• MSA coating solution was coated onto a 60 micron thick cast polypropylene (CPP) film by knife coating and dried in the oven at 100 degree C for 5 minutes.
• CPP cast polypropylene
• Acrylic MSA layer formed on the CPP film by coating was transferred to the reflective side of a specularly reflective film (ESR, manufactured by 3M) using a hand roller and then the optically diffusive film having a non-woven layer was laminated to the acrylic MSA layer using a hand roller.
• ESR specularly reflective film
• the Specular reflectance (average of 400-800nm) was measured using a_Spectrophotometer UV- 3 lOOPC / MPC-3100 (Shimadzu Corporation).
• the Total light reflectance (average of 400-800nm) was measured using a Spectrophotometer U- 4100 (Hitachi High Technology). d) Measurement of Luminance
• Spectroradiometer CS-1000 Konica Minolta was used to measure the center luminance.
• Sample which is made by lamination with common plane OCA was prepared using same Nonwoven material, ESR and 7029, 15 micron thick OCA (manufactured by Teraoka Seisakusho, Co., LTD).
• the MSA contact area ratio, total light reflectance, specular reflectance, and relative luminance of each sample are listed in below table.
• diffusive reflective film assembly including a MOF based specular reflective film and properly designed optically diffusive film including a non-woven layer shows high diffuse reflection performance with high luminance when both components are laminated with acrylic microsphere adhesive (MSA) and the contact area ratio between MOF based specular reflective film and MSA is less than 20%, less than 10% being more desirable.
• MSA acrylic microsphere adhesive
• the specularly reflective film (40) is bonded to the optically diffusive film (50) via locally applied heat and pressure lamination at at least one (81) of the bonded locations.
• the bonding locations (60) form a bonding pattern of a plurality of spaced apart bonding areas (Ab). Each bonded location (60) defines a bonded area (Ab) of a major surface (41) of the specularly reflective film (40).
• the total bonding area (Ab) may be less than about 10%, or less than about 5%, or less than about 4%.
• Tepyrus TA04PN manufactured by Teijin
• Tepyrus TJ04CN manufactured by Teijin
• 70wt% Tepyrus TA04PN and 30wt% of Tepyrus TJ04CN may be used as fiber ingredient.
• Fiber setting and calendering process may be used for making non-woven optically diffusive film (50) having a thickness of about 34 micron with a total transmittance of about 64%.
• Structured tools may be used for spot discontinuous heat and pressure lamination to obtain the desired bonding.
• the structured tools may be a pyramidal shape tool or a trapezoidal prism shape tool, or a combination of both.
• the structured area of the structured tool is 120mm x 120mm and the size of the non-woven layer is 150mm x 150mm. Both upper and lower stages were heated at same temperature.
• the specularly reflective film and the non-woven optically diffusive layer were not pre-heated.
• the optically diffusive film having non-woven fibers and the specularly reflective film (ESR, manufactured by 3M) were stacked and pressed with heat using the structured tool at a temperature of about 120-150 degrees and a pressure of about 10-50 KN.
• the nonwoven material was heat laminated to 50micron thick PET film (E4100, TOYOBO CO., LTD.) instead of ESR, using structured tool. After the heat lamination, the photograph of the surface of PET film was taken using microscope (VK-X100, Keyence Corporation) at extended magnification (10 times). Only the portion of core-sheath fiber could adhere to the PET film and this area looked darker grey color than the other area when the laminated sample was seen from PET film side.
• the Specular reflectance (average of 400-800nm) was measured using a_Spectrophotometer UV- 3 lOOPC / MPC-3100 (Shimadzu Corporation).
• the Total light reflectance (average of 400-800nm) was measured using a Spectrophotometer U- 4100 (Hitachi High Technology). d) Measurement of Luminance
• Spectroradiometer CS-1000 Konica Minolta was used to measure the center luminance. Spot heat laminated sample was too small to assemble to the testbed. Therefore, 2 sample pieces were connected using ESR with adhesive tape. The ESR with adhesive tape was applied to the backside of the reflective film.
• each diffusive reflective film sample which is made by spot heat lamination with structured tool is compared to that of the sample which is made by heat lamination with plane tool. “Relative luminance” calculated using below formula is used as the index.
• the contact area ratio, total light reflectance, specular reflectance, and relative luminance of each sample are listed in below table.
• diffusive reflective fdm assembly including a multiple optical fdm (MOF) based specular reflective fdm and properly designed optically diffusive fdm including a non-woven layer shows high diffuse reflection performance with high luminance when the non-woven material contains core-sheath fiber more than 10%, and both components are laminated by spot (discontinuous) heat lamination with structured tool, and the contact area ratio between the non-woven material and the MOF based specular reflective fdm is less than 5%.
• MOF optical fdm

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