WO2014192194A1 - ライトボックス - Google Patents
ライトボックス Download PDFInfo
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- WO2014192194A1 WO2014192194A1 PCT/JP2013/084280 JP2013084280W WO2014192194A1 WO 2014192194 A1 WO2014192194 A1 WO 2014192194A1 JP 2013084280 W JP2013084280 W JP 2013084280W WO 2014192194 A1 WO2014192194 A1 WO 2014192194A1
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- WIPO (PCT)
- Prior art keywords
- light
- light source
- box according
- extraction surface
- led
- Prior art date
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V7/00—Reflectors for light sources
- F21V7/04—Optical design
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- 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
- G02B6/0096—Light 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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2103/00—Elongate light sources, e.g. fluorescent tubes
- F21Y2103/10—Elongate light sources, e.g. fluorescent tubes comprising a linear array of point-like light-generating elements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2105/00—Planar light sources
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2115/00—Light-generating elements of semiconductor light sources
- F21Y2115/10—Light-emitting diodes [LED]
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- 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
- the present invention relates to a light box used for a backlight of a display device, a lighting fixture, and an electric signboard.
- LEDs Light Emitting Diodes
- LEDs have a longer life than incandescent bulbs, fluorescent lamps, and the like, and in recent years, improvement in luminous efficiency, higher output, and lower prices are progressing.
- LEDs have been widely used as light sources of light boxes used for backlights of display devices, lighting fixtures, electric signboards, and the like.
- the LED is a point light source, in order to use it for a light box, it is necessary to convert the point emission by the LED into uniform surface emission.
- an edge light system using a light guide plate, a direct type system in which LEDs are arranged in a planar shape, and the like are known.
- the edge light method is a method in which LED light is irradiated to the end face of a light guide plate made of a transparent acrylic plate or the like, and the light is repeatedly reflected inside the light guide plate and taken out from a wide surface of the light guide plate. .
- Dots for diffusing light are distributed in the light guide plate, and light traveling inside the light guide plate hits the dots and changes direction so that it strikes a wide surface of the light guide plate at an angle smaller than the total reflection angle. The light is emitted to the outside (see, for example, Patent Document 1). According to this method, uniform surface light emission can be easily obtained and a large area can be dealt with.
- the direct type method is a method in which a plurality of LEDs are arranged on the bottom surface of a light box and light is irradiated toward a light extraction surface to which a diffusion plate is attached (for example, see Patent Document 2).
- the luminance increases at the portion corresponding to the front of each LED, and uneven luminance occurs. Therefore, this method cannot use LEDs with a large amount of light, and it is necessary to arrange a large number of LEDs with a relatively small amount of light.
- a technology called a lens method or a light diffusing reflector method has been developed as an improvement of the direct type.
- a wide-angle lens or a diffusion lens is attached to the LED in order to suppress the front luminance of the LED in the direct type system as described above (see, for example, Patent Document 3).
- the lens is arranged between the LED and the diffusion plate, the light box becomes thick, and the cost for the lens increases.
- the entire light box is made up of a reflection plate, and surface light emission is made uniform by distributing large and small through holes in the reflection plate on the light extraction surface side (see, for example, Patent Document 4). ).
- Patent Document 4 the through hole on the light extraction surface includes a very small hole of 0.3 mm.
- the processing is expensive.
- the present invention has been made in view of the above points, and the object of the present invention is that it can be manufactured at low cost without using expensive parts, and the uniformity of the light emission state of the light extraction surface is high.
- An object of the present invention is to provide a light box that can suppress a loss of irradiation light from a light source.
- a light box for reflecting light emitted from a light source inside a housing and taking out light from the light extraction surface of the housing as surface light emission a) a housing having a facing surface facing the light extraction surface, and a peripheral surface extending from a peripheral edge of the facing surface and surrounding a space between the light extraction surface and the facing surface; b) a light source disposed on the peripheral surface and irradiating the space with light; c) a spread angle regulating means for regulating a spread angle of light emitted from the light source in a plane that includes the optical axis of the light source and is orthogonal to the light extraction surface; It is characterized by having.
- LED is typically used as a light source in the present invention
- other light sources such as a light bulb, a fluorescent lamp, a cold cathode tube, and the like can also be used.
- the light box having the above-described configuration is configured to reflect the irradiation light from the light source inside the housing and extract the reflected light from the light extraction surface. Therefore, it is not necessary to use an expensive light guide plate as in the above-described edge light method, and furthermore, since surface emission can be obtained with a smaller number of LEDs than in the direct irradiation method, it can be manufactured at low cost. it can. Furthermore, by providing a spread angle regulating means for regulating the spread angle of the light emitted from the light source, it is possible to prevent the light emitted from the light source from entering the light extraction surface or the opposite surface in the immediate vicinity of the light source. it can. Thereby, it is possible to prevent the light emission intensity on the light extraction surface from increasing only in the vicinity of the light source and to obtain uniform surface light emission.
- the light box according to the present invention it is preferable that light from the light source is incident on the facing surface at an incident angle of 70 ° or more.
- the incident angle of light on the opposing surface is increased in this way, the emission angle of the light reflected by the opposing surface also increases.
- most of the light incident on the opposing surface from the light source does not go to the light extraction surface in the immediate vicinity, but travels further into the housing. Thereby, it is possible to prevent the amount of light incident on the light extraction surface in a region far from the light source from being reduced, and to obtain more uniform surface light emission.
- the facing surface of the housing When the facing surface of the housing is flat and the peripheral surface is substantially perpendicular to the facing surface, part of the light emitted from the light source and reaching the back of the housing has a small incident angle. Is incident on. Since this light is reflected on the peripheral surface at a small emission angle and returns to the front side of the housing, the amount of light reaching the light extraction surface on the back side of the housing is reduced accordingly. Therefore, it is desirable that the light box according to the present invention be provided with a slope that approaches the light extraction surface as the distance from the light source increases in a region or the facing surface of the peripheral surface facing the light source.
- the light source is installed so as to be inclined so as to be separated from the light extraction surface as its optical axis is moved away from the light source.
- the light box according to the present invention is provided with an inclination in the region adjacent to the light source on the peripheral surface or the region on the facing surface adjacent to the region so as to approach the light extraction surface as the light source is approached. It is desirable that
- the divergence angle restricting means has a cross-sectional shape in a plane that includes the optical axis of the light source and that is orthogonal to the light extraction surface, toward the opposite side of the light traveling direction on the optical axis.
- the cover may be a substantially V-shaped or U-shaped cover that is convex.
- the divergence angle regulating means may be a lens.
- the above-mentioned cover and lens are attached directly to the LED chip or attached to the LED substrate, and are not attached directly to the LED or LED substrate, but to another support method. It is good also as a structure which maintains the positional relationship with LED.
- the facing surface and the peripheral surface are integrally formed.
- the housing has a plurality of protrusions that reflect light from the light source on at least the facing surface.
- the light source is preferably an LED array in which a plurality of LED elements are arranged in a one-dimensional manner.
- the light extraction surface has a polygonal shape, and is located at a position corresponding to one or a plurality of sides of the polygon as viewed from a direction perpendicular to the light extraction surface. It is desirable that the light source is arranged.
- the light extraction surface has a polygonal shape, and the light source is arranged at one or more corners of the polygon as viewed from a direction perpendicular to the light extraction surface. It is desirable that
- a diffusion plate for diffusing light emitted from the light extraction surface is disposed on the light extraction surface.
- the present invention it is possible to provide a light box that can obtain surface light emission with high uniformity with little loss of irradiation light from a light source and can be manufactured at low cost.
- the perspective view which shows the outline of the light box which concerns on 1st Embodiment of this invention. It is a figure which shows the reflective nozzle in the said light box, Comprising: (a) is a perspective view, (b) is a top view, (c) is a side view. It is a schematic diagram which shows the path
- the perspective view which shows the structure which provided the diffusion plate in the said light box.
- the perspective view which shows the example in the case of attaching LED to the corner of a light box.
- the perspective view which shows the example in the case of attaching LED to four corners and two sides of a light box.
- the perspective view which shows the structure of the light box which concerns on 2nd Embodiment of this invention. It is a figure which shows the said light box, Comprising: (a) is a top view, (b) is a side view. It is a figure which shows the reflective nozzle in the said light box, Comprising: (a) is a perspective view, (b) is a top view, (c) is a side view.
- FIG. 1 It is a schematic diagram which shows the course of the light from LED, Comprising: (a) shows the case where a side surface is perpendicular
- FIG. 1 is a perspective view of a light box according to a first embodiment of the present invention.
- the vertical direction is defined with reference to FIG.
- the light box according to the present embodiment includes a housing 100 and an LED 120.
- the casing 100 has a bottom surface 111 and a side surface 112, and has a shallow box shape with an open top surface.
- the bottom surface 111 corresponds to the facing surface in the present invention
- the side surface 112 corresponds to the peripheral surface.
- An opening 113 is provided at one place on the side surface 112, and the light emitted from the LED 120 attached to the outside of the housing 100 is emitted from the opening 113 to the inside of the housing 100.
- the light irradiated to the inside of the housing 100 is reflected by the bottom surface 111 and the side surface 112 of the housing 100 and is extracted from the top surface to the outside.
- the upper surface is referred to as a light extraction surface.
- At least the inner surface (reflection surface) of the housing 100 is made of a material having a reflectance in the visible light range of 85% or more and a total light transmittance of 10% or less.
- molded by methods, such as a process, can be used.
- thermoplastic resins that can be used include acrylic resins, methacrylic resins, polyolefins, polyamides, polyesters, polycarbonates, styrenic resins, polyethers, polyurethanes, polyphenylene sulfides, polyester amides, polyether esters, polyvinyl chlorides. , Modified polyphenylene ether, polyarylate, polysulfone, polyimide, polyetherimide, polyamideimide, or a copolymer containing these as main components, or a mixture thereof, but is not limited thereto. .
- a sheet material fine foam reflection sheet
- the fine foam reflection sheet an acrylic foam sheet (for example, “Diffle” manufactured by Duela Co., Ltd.) manufactured by a supercritical fine foam sheet molding process and having a visible light diffuse reflectance of 90% or more is used.
- the diffuse reflectance of the visible light means the ratio of the diffuse reflectance flux to the incident light flux, measured at a wavelength of 550 nm with a self-recording spectrophotometer, and diffused on a white plate in which fine powder of barium sulfate is hardened. This is a value obtained as a relative value with a reflectance of 100%.
- the self-recording spectrophotometer for example, UV-3100PC (manufactured by Shimadzu Corporation) can be used.
- the housing 100 preferably has a bottom surface 111 and a side surface 112 integrally formed.
- Integral molding is a method like injection molding, in which resin is injected with the same mold so that the bottom and side surfaces are integrated, or sheet-like material is softened by heat and then vacuum or compressed air is used.
- the bottom surface and the side surface are formed into an integral shape by a method called vacuum forming in which a sheet is pressed against a mold with the pressure of
- integrally molding it is possible to prevent a gap from being formed between the bottom surface 111 and the side surface 112, and it is possible to send light that has entered the housing 100 to the light extraction surface 110 without leaking.
- the light box according to the present embodiment further includes a reflection nozzle 130 (corresponding to a cover in the present invention) attached to the LED 120 as a characteristic component of the present invention.
- a reflection nozzle 130 (corresponding to a cover in the present invention) attached to the LED 120 as a characteristic component of the present invention.
- the function of the reflection nozzle 130 will be described.
- the light emitted from the LED is emitted from the LED surface at a spread angle of about 90 ° to 130 °.
- a large amount of light travels toward the light extraction surface 110 in the vicinity of the LED 120 ( FIG. 3 (a)).
- the reflection nozzle 130 as shown in FIG.
- the LED 120 is mounted on the LED 120 to limit the light spreading angle in the vertical direction (FIG. 3B). Thereby, the light reaching the light extraction surface 110 and the bottom surface 111 in the vicinity of the LED 120 can be reduced, and the light from the LED 120 can reach a farther region in the housing 100. As a result, since the light from the LED 120 reaches the entire area within the housing 100, it is possible to obtain uniform surface emission on the light extraction surface 110.
- the reflection nozzle 130 has a shape in which the opening angle is small in the vertical direction and the opening angle is widened in the horizontal direction.
- an LED attachment hole 131 for exposing the light emitting portion of the LED 120 into the reflection nozzle 130 is provided in the central portion of the reflection nozzle 130.
- the cross-sectional shape in the vertical direction of the reflection nozzle 130 is set so that the irradiation angle of the emitted light from the LED 120 is 40 ° or less, preferably 30 ° or less, and the light emitted from the LED 120 is irradiated at an angle close to parallel light rays. I will let you.
- the cross-sectional shape is preferably a curve close to a part of an ellipse or a curve close to a parabola, although it depends on the light emission angle of the LED 120 itself.
- the cross-sectional shape in the left-right direction is designed to an appropriate value according to the dimensions of the housing 100 and the mounting position of the LED 120. Specifically, it is desirable that the irradiation angle of the light emitted from the LED 120 is 80 ° to 140 °. Thereby, light can be irradiated in a direction parallel to the light extraction surface 110 with a sufficient spread angle.
- the LED 120 equipped with such a reflective nozzle 130 is attached to the housing 100 such that its optical axis is parallel to the light extraction surface 110 (and the bottom surface 111), the light from the LED 120 is reflected on the bottom surface of the housing 100.
- the incident angle when directly entering 111 is 70 ° or more.
- the emission angle of the light reflected by the bottom surface 111 is increased accordingly.
- the light emitted from the LED 120 can travel to the back of the housing 100, and a sufficient amount of light can be obtained even in a region far from the LED 120.
- thermoplastic resin may be molded by a method such as injection molding, sheet bending, or sheet molding.
- thermoplastic resins include acrylic resins, methacrylic resins, polyolefins, polyamides, polyesters, polycarbonates, styrenic resins, polyethers, polyurethanes, polyphenylene sulfides, polyester amides, polyether esters, polyvinyl chlorides.
- the inner surface (reflective surface) of the reflective nozzle 130 may be plated with metal. Further, the reflection nozzle 130 may be made of the same material as that of the housing 100, and both may be integrally formed. Thereby, it is possible to prevent light from leaking between the reflective nozzle 130 and the housing 100.
- a diffusion plate 140 for diffusing light emitted from the light extraction surface can be installed on the light extraction surface of the light box.
- the diffusion plate 140 needs to be provided.
- the LED 120 is provided only at one place on the side surface 112 of the housing 100. However, as shown in FIGS. (Refer nozzles are omitted for simplification in FIGS. 5 to 7).
- the number and position of the LEDs 120 can be appropriately set according to the shape and dimensions of the housing 100, for example, the ratio of length to width.
- the two LEDs 120 are arranged at two opposite corners, and in the example of FIG. 6, they are arranged at two adjacent corners.
- the LEDs 120 are provided at two opposite corners of the four corners of the housing 100 and the four side surfaces 112.
- the arrangement as shown in FIG. 7 is effective when the size of the casing 100 is large in the vertical direction or the horizontal direction, and the amount of light is insufficient in the central portion only by irradiation from the four corners.
- FIG. 8 is a perspective view of the light box according to the present embodiment
- FIG. 9 is a plan view and a side view of the light box according to the embodiment.
- an LED array 122 in which a plurality of LED elements 121 are arranged in a row as a light source is attached to one of the side surfaces 112 of the housing 100.
- An opening (not shown) is provided in the side surface 112 to which the LED array 122 is attached, and light from each LED enters the housing 100 through the opening.
- a long reflective nozzle 130 as shown in FIG. 10 is used as a means for regulating the spread angle of light from the LED array 122.
- the reflective nozzle 130 has a length that can cover the entire longitudinal direction of the LED array 122, and a long hole-shaped LED is attached to expose the light emitting portion of each LED element 121 in the reflective nozzle 130.
- a hole 131 is provided.
- the cross-sectional shape of the reflection nozzle 130 in the vertical direction is set so that the irradiation angle of the emitted light from the LED array 122 is 40 ° or less, preferably 30 ° or less, as in the first embodiment.
- this cross-sectional shape also depends on the light emission angle of the LED array 122 itself, it is desirable that the cross-sectional shape be a curve close to a part of an ellipse or a curve close to a parabola.
- the cross-sectional shape in the left-right direction is such that the spread angle of the emitted light from the LED array 122 is 0 ° to 40 ° depending on the ratio of the length of the LED array 122 and the side surface 112 to which the LED array 122 is attached. It is desirable to do so.
- the light box of the present embodiment has a feature that a part of the bottom surface 111 and the side surface 112 of the housing 100 is inclined.
- a region close to the LED array 122 (on the left side in FIG. 11) along the optical axis of the LED element 121 located in the center of the LED array 122 is located on the front side, and a region far from the LED array 122 (on the right side in FIG. 11). This is called the back (in FIG. 11, the reflection nozzle is omitted for simplification).
- the inclination may be a shape such that the inner surface (the bottom surface 111 and the side surface 112) of the housing approaches the light extraction surface 110 as it moves away from the LED array 122, but is desirably located at the center of the LED array 122.
- the optical element When viewed in a cross section including the optical axis of the LED element 121 and perpendicular to the light extraction surface 110, the optical element has a curved surface like a part of an ellipse, and the optical axis of the LED element 121 is projected onto the inner surface of the housing. It is assumed that the curvature of the curve obtained in this manner monotonously decreases from the LED element 121 side.
- the bottom surface is set such that variations in incident angles ( ⁇ 1, ⁇ 2, ⁇ 3,... In FIG. 11B) of light directly incident on the bottom surface 111 and the side surface 112 from the LED element 121 are within 10 °. It is preferable to design the shape. Thereby, the reflected light from the bottom surface 111 can be uniformly incident on the entire light extraction surface 110.
- the LED array 122 may be attached by being inclined downward so that the optical axis of each LED element 121 is separated from the light extraction surface 110 as the distance from the LED element 121 increases.
- the reflection nozzle is omitted for simplification). Thereby, the light directly incident on the light extraction surface 110 from the LED array 122 can be reduced.
- the amount of light reflected by the bottom surface 111 in the vicinity of the LED array 122 and incident on the light extraction surface 110 is increased. Therefore, in order to prevent this, as shown in FIG. 12, it is desirable to provide an inclination on the front side of the housing 100 such that the bottom surface 111 and the side surface 112 approach the light extraction surface 110 as the LED array 122 is approached.
- Such an inclination can increase the incident angle of light that directly enters the bottom surface 111 or the front side surface 112 from the LED 120.
- the emission angle of the reflected light from the bottom surface 111 or the side surface 112 also increases, so that the reflected light can reach the back of the housing 100.
- the inclination is preferably designed so that the incident angle ⁇ of light directly incident on the bottom surface 111 or the near side surface 112 from the LED element 121 is 70 ° or more.
- a plurality of protrusions 150 are provided on the bottom surface 111 of the light box according to the present embodiment.
- Each of these protrusions 150 has a shape that protrudes from the bottom surface 111 of the housing 100 toward the light extraction surface 110, and light rays that travel along the bottom surface 111 of the housing 100 as shown in FIG. 13. Is intended to be reflected toward the light extraction surface 110.
- the shape of the protrusion 150 is not particularly limited, and may be any shape such as a rectangular parallelepiped, a pyramid shape, a hemispherical shape, and the like. However, the hemispherical shape as shown in FIG.
- the height of the protrusion 150 is preferably about 0.5 mm to 3 mm.
- the number and arrangement of the protrusions 150 are appropriately set so that the illuminance distribution on the light extraction surface 110 is optimal. Specifically, it is conceivable that the portion near the LED array 122 is likely to be bright and therefore the number of protrusions 150 is reduced, and the portion far from the LED array 122 is likely to be dark and the number of protrusions 150 is increased.
- the shape of the bottom surface 111 and the side surface 112 of the housing 100 may be changed stepwise as shown in FIG. 11B in addition to changing continuously as shown in FIG. Further, a stepped step may be provided as shown in FIG. Note that in the configuration in which such an inclination is provided, the boundary between the bottom surface 111 and the side surface 112 of the housing 100 may not be clear.
- the LED can be attached to any position on the side surface of the housing even in the configuration in which the slope and the protrusion are provided on the bottom surface.
- FIG. 16 shows an example in which LEDs 120 are provided at the four corners of the housing 100 (for the sake of simplicity, the reflective nozzle is omitted). In this case, the light beam from each LED 120 travels from the four corners toward the center of the housing 100. Also in this example, each LED 120 is attached so as to be inclined downward so that the optical axis is separated from the light extraction surface 110 as the distance from the LED 120 increases.
- the inner surface (that is, the bottom surface 111 and the side surface 112) of the casing 100 has a shape in which the central portion and the four corners are raised, in other words, four quadrangular pyramids with the apex facing downward are arranged two by two.
- the shape is different.
- a lens 160 is disposed in front of the LED 120 as shown in FIG. 17, and the spread angle of light from the LED 120 is regulated by the lens 160. You may make it do.
- the luminance distribution at this time was as shown in Table 1.
- the luminance distribution is expressed as a ratio of each region when the luminance of each region obtained by dividing the light emitting surface into five parts in the vertical direction and the horizontal direction is measured and the central part is 100% (hereinafter the same). ).
- Example 1 The light box having the configuration shown in FIGS. 8 and 9 was subjected to the same measurement as described above. Specifically, the liquid crystal monitor has a light extraction surface of 476 mm in width and 270 mm in length corresponding to a size of 21.5 inches, and the bottom surface and side surfaces are vacuum-molded with a reflection sheet (Duela Co., Ltd. “Diffure” 400 ⁇ m) (molding temperature 170).
- the bottom surface of the housing was formed so as to draw a gentle curved surface from the side surface on which the LED was mounted toward the side surface facing the surface, and hemispherical projections with a diameter of 2 mm were distributed on the inner surface. Further, a diffusion sheet (thickness 0.2 mm) was attached to the light extraction surface.
- the overall luminance was 3449.1 cd / m 2 . Further, the luminance distribution at this time was as shown in Table 2.
- the overall luminance was improved by 9.4% compared to the comparative example. From this, it was confirmed that the light loss at the light guide plate was large in the light guide plate method of the comparative example, whereas the light loss was suppressed in the method of the present invention.
- the luminance distribution although the luminance was high in the region close to the LED light source (first row in Table 2), it was confirmed that the variation in luminance was smaller in the other portions than in the comparative example.
- Example 2 The light box of Experimental Example 1 was prepared by removing the reflective nozzle attached to the LED, and the LED was caused to emit light. As a result, the light emission in the vicinity of the LED light source became too strong, and it became dark from the center of the light box to the opposite side of the light source.
- Example 3 An LED was produced by exchanging the bottom surface of the light box of Experimental Example 1 with a flat plate (without protrusions) parallel to the light extraction surface. As a result, the incident angle of the light beam hitting the bottom reflector on the side closer to the LED was less than 50 °, and the reflected light was directed directly to the light extraction surface, resulting in an increase in brightness near the LED. Further, since the luminance was high even on the side far from the light source, the luminance distribution was unbalanced with the dark central portion as a whole. This is presumably because the direction of light does not change due to the protrusion, and the light toward the light extraction surface is reduced at the center of the light box.
- Example 4 A light box in which the bottom surface of the light box of Experimental Example 1 was replaced with one having no protrusion was created, and the LED was caused to emit light. As a result, the side near the LED and the central part were dark, and the side far from the LED was bright.
- Example 7 As shown in FIG. 5, two LEDs equipped with reflective nozzles were mounted on the diagonal of a light box having a flat bottom surface to emit light. As a result, the light quantity of the LED was insufficient and the corner portion where the LED was not mounted became dark, but the uniformity of the central portion was not bad. Moreover, the optimal luminance distribution was obtained when the LED irradiation direction was slightly shifted from the center.
- Example 8 An LED light emission experiment was performed on the light box of Experimental Example 7 from which one LED was removed. In addition, LED was installed so that an optical axis might go to the center of a light box. As a result, the light quantity of the LED was insufficient, and only the central portion of the light box was brightened, but a good light emission state was obtained at the central portion.
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Abstract
Description
光源からの出射光を筐体の内部で反射させ、該筐体の光取り出し面から面発光として取り出すためのライトボックスであって、
a) 光取り出し面に対向する対向面と、該対向面の周縁から延出し、前記光取り出し面と前記対向面の間の空間を囲繞する周面とを備えた筐体と、
b) 前記周面に配置され、前記空間に光を照射する光源と、
c) 前記光源の光軸を含み前記光取り出し面と直交する面内における前記光源からの出射光の広がり角を40°以下に規制する広がり角規制手段と、
を有することを特徴としている。
そこで、本発明に係るライトボックスは、前記周面の前記光源に対向する領域又は前記対向面に、前記光源から遠ざかるにつれて前記光取り出し面に近づくような傾斜を設けたものとすることが望ましい。
そこで、本発明に係るライトボックスは、前記周面の前記光源に隣接する領域又は該領域に隣接する前記対向面上の領域に、該光源に近づくにつれて前記光取り出し面に近づくような傾斜を設けたものとすることが望ましい。
SAMSUNG社製のカラー液晶モニター21.5インチ(BX2250)のバックライト部分を取り出し、導光板及び拡散シート(厚さ0.2mm)を装着した状態で発光させ、その際の全体の輝度及び輝度分布を測定した。輝度測定には有限会社ハイランド製RISA-Color ONE/3 (3CCD 1/3in 12.5-50mmズームレンズ装着)を使用した。
図8、図9に示すような構成を有するライトボックスについて上記同様の測定を行った。具体的には、液晶モニター21.5インチサイズに相当する横476mm、縦270mmの光取り出し面を持ち、底面及び側面が反射シート(株式会社デュエラ製「ディフューレ」400μm)で真空成形(成形温度170℃)された一体型の筐体を備えたライトボックスを製作し、更に前記反射シートで作成した反射ノズルを比較例で使用したものと同じ光源(LEDを直線状に並べたもの)に取り付け、これをライトボックスの長辺側の側面に装着して発光させた。筐体の底面は、LEDが装着された側面から当該面に対向する側面に向かってなだらかな曲面を描くように形成し、その内表面には直径2mmの半球状の突起を分布させた。更に、光取り出し面には拡散シート(厚さ0.2mm)を装着した。
実験例1のライトボックスからLEDに装着した反射ノズルを外したものを作成し、LEDを発光させた。その結果、LED光源付近の発光が強くなりすぎて、ライトボックスの中央から光源の反対側にかけては暗くなってしまった。
実験例1のライトボックスの底面を光取り出し面と平行な平板(突起の無いもの)に交換したものを作成し、LEDを発光させた。その結果、LEDに近い側で底面の反射板に当たる光線の入射角が50°未満となり、反射光が光取り出し面に直接向かうため、LED近傍での輝度が高くなってしまった。また、光源から遠い側でも輝度が高くなったため、全体としては中央部が暗くバランスの悪い輝度分布となった。これは、突起によって光の方向が変わることがないため、ライトボックスの中央部分で光取り出し面に向かう光が減少したためと考えられる。
実験例1のライトボックスの底面を突起の無いものに交換したものを作成し、LEDを発光させた。その結果、LEDに近い側と中央部分が暗く、LEDから遠い側が明るくなった。
図16のライトボックスの四隅に反射ノズル付きのLEDを装着して発光させた。その結果、長辺側の中央端部が若干暗くなるもののおおむね均一な面発光が得られた。
実験例5のライトボックスの各長辺の中央部分にLEDを追加して発光させた。その結果、上記長辺側の中央端部は逆に明るさが強くなったものの、全体的には良好な発光状態となった。
図5のように底面を平板状としたライトボックスの対角に、反射ノズルを装着した2個のLEDを装着して発光させた。その結果、LEDの光量が足りずLEDを装着していない角の部分が暗くなってしまったが、中央部分の均一性は悪くなかった。また、LEDの照射方向を中央より若干ずらしたときに最適な輝度分布が得られた。
実験例7のライトボックスからLEDを一つ取り外したものについて、LEDの発光実験を行った。なお、LEDは光軸がライトボックスの中央に向かうように設置した。その結果、LEDの光量が足りず、ライトボックスの中央部分までしか明るくならなかったものの、中央部分では良好な発光状態が得られた。
110…光取り出し面
111…底面
112…側面
113…開口部
120…LED
122…LEDアレイ
130…反射ノズル
140…拡散板
150…突起
160…レンズ
Claims (15)
- 光源からの出射光を筐体の内部で反射させ、該筐体の光取り出し面から面発光として取り出すためのライトボックスであって、
a) 光取り出し面に対向する対向面と、該対向面の周縁から延出し、前記光取り出し面と前記対向面の間の空間を囲繞する周面とを備えた筐体と、
b) 前記周面に配置され、前記空間に光を照射する光源と、
c) 前記光源の光軸を含み前記光取り出し面と直交する面内における前記光源からの出射光の広がり角を40°以下に規制する広がり角規制手段と、
を有することを特徴とするライトボックス。 - 前記光源からの光が70°以上の入射角度で前記対向面に入射することを特徴とする請求項1に記載のライトボックス。
- 前記周面の前記光源に対向する領域又は前記対向面に、前記光源から遠ざかるにつれて前記光取り出し面に近づくような傾斜を設けたことを特徴とする請求項1又は2に記載のライトボックス。
- 前記光源を、その光軸が該光源から遠ざかるにつれて前記光取り出し面から離れるように傾けて設置したことを特徴とする請求項1~3のいずれかに記載のライトボックス。
- 前記周面の前記光源に隣接する領域又は該領域に隣接する前記対向面上の領域に、該光源に近づくにつれて前記光取り出し面に近づくような傾斜を設けたことを特徴とする請求項1~4のいずれかに記載のライトボックス。
- 前記広がり角規制手段が、前記光源の光軸を含み前記光取り出し面と直交する面における断面形状が、前記光軸上における光の進行方向の逆側に向かって凸となるような略V字型又は略U字型であるカバーから成るものであることを特徴とする請求項1~5のいずれかに記載のライトボックス。
- 前記広がり角規制手段がレンズから成るものであることを特徴とする請求項1~5のいずれかに記載のライトボックス。
- 前記対向面と前記周面が一体に成形されていることを特徴とする請求項1~7のいずれかに記載のライトボックス。
- 前記筐体が、少なくとも前記対向面上に前記光源からの光を反射する複数の突起を有することを特徴とする請求項1~8のいずれかに記載のライトボックス。
- 前記光源が、複数個のLED素子を一次元状に配列させたLEDアレイであることを特徴とする請求項1~9のいずれかに記載のライトボックス。
- 前記光取り出し面が多角形形状を有しており、該光取り出し面に垂直な方向から見て前記多角形の1つ又は複数の辺に相当する位置に前記光源が配置されていることを特徴とする請求項1~10のいずれかに記載のライトボックス。
- 前記光取り出し面が多角形形状を有しており、該光取り出し面に垂直な方向から見て前記多角形の1つ又は複数の角に前記光源が配置されていることを特徴とする請求項1~11のいずれかに記載のライトボックス。
- 前記光取り出し面に、該光取り出し面から出射する光を拡散させるための拡散板を配置したことを特徴とする請求項1~12のいずれかに記載のライトボックス。
- 請求項1~13のいずれかに記載のライトボックスを使ったことを特徴とするディスプレイ装置のバックライト。
- 請求項1~13のいずれかに記載のライトボックスを使ったことを特徴とする照明器具。
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