JP2006032370A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED To provide a light emitting device capable of uniform and high luminance light emission.
The light guide includes a light source, a light incident surface 101a on which light from the light source is incident, and a light emitting surface 101b having an optical shape such that the emitted light has predetermined optical characteristics. The optical shape of the light emitting surface 101b is a first surface, a second surface,..., N (n ≧ n) in a direction away from the optical axis of the optical shape. 1) in order, and an angle θ _n (−90 ° ≦ θ _n ≦ 90 °) formed by the light incident surface 101b and the nth surface satisfies θ _n ≦ θ _{n + 1.} Device.
[Selection] Figure 2

Description

  The present invention relates to a light emitting device used for a liquid crystal backlight, a push button of a switch, a nameplate, various display boards, and the like, and more particularly, to a light emitting device capable of uniform light emission in a planar light source used for a liquid crystal backlight. .

  Conventionally, in a planar light source composed of a light emitting diode and a light guide that receives light from the light emitting diode and is emitted from a predetermined direction, the light is guided from the light emitting diode uniformly. There has been proposed a light-emitting device having a concavo-convex shape on a light emission observation surface of a body. For example, a light emitting device disclosed in Japanese Patent Application Laid-Open No. 2002-298629 forms a recess whose inner diameter gradually increases with respect to a light emission observation surface of a light guide plate located immediately above a light emitting diode. Thereby, the light from the light emitting diode is reflected by the inner wall surface of the recess and is diffused in the light guide. That is, in the light guide plate of the light emitting device disclosed in this patent document, the light emitted from the lower surface of the light guide plate facing the light emitting surface of the light emitting diode is totally reflected by the recessed portion, and the upper surface of the light guide plate (light emission observation surface). ) Has an optical characteristic such that the light travels in a direction parallel to. Therefore, substantially uniform light emission can be observed from the light emission observation surface.

JP 2002-298629A.

  However, in the light emitting device disclosed in Japanese Patent Application Laid-Open No. 2002-298629, the light incident on the inner wall surface of the depression is totally reflected at the depression as described above, and the traveling direction is made to the emission observation surface of the light guide plate. And proceed in parallel directions. Therefore, when the light guide is observed from the side having the dent, the dent portion becomes darker than the other portions. In addition, the light reflected by the inner wall surface of the depression is repeatedly reflected inside the light guide plate, and may be attenuated without being emitted from the light emission observation surface. Thus, the light emitting device according to the prior art cannot emit light with high brightness and uniformity.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting device that can emit light with high luminance and uniformity.

In order to achieve the above object, a light-emitting device according to the present invention includes a light source, a light incident surface on which light from the light source is incident, and light having an optical shape such that the emitted light has predetermined optical characteristics. A light guide having an emission surface, wherein the optical shape of the light emission surface is a first surface, a second surface, ... in a direction away from the optical axis of the optical shape. It is assumed that an angle θ _n (−90 ° ≦ θ _n ≦ 90 °) between the light incident surface and the n th surface satisfies θ _n ≦ θ _{n + 1.} Features. Thereby, it can be set as the light-emitting device which carries out high-intensity and uniform light emission.

  Moreover, it is preferable that the said light-projection surface has a protruding part with a triangular cross section. Further, the light emitting surface has concentrically arranged protrusions having the first surface, the second surface,..., The nth (n ≧ 1) surface when viewed from the optical axis direction. It is preferable that

  In addition, the light emitting surface further includes a surface adjacent to any one of the first surface, the second surface,..., The nth (n ≧ 1) surface and substantially parallel to the light incident surface. Can have.

  The light diffuser diffuses the light emitted from the light guide. Thus, a light emitting device that emits light more uniformly can be obtained. The light source is preferably a light emitting diode. Thus, a light emitting device with high luminance and low power consumption can be obtained.

  The present invention can provide a light emitting device capable of emitting light with high brightness and uniformity.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the form shown below illustrates the light emitting device for embodying the technical idea of the present invention, and the present invention does not limit the light emitting device to the following. Further, the size and positional relationship of the members shown in the drawings are exaggerated for clarity of explanation.

In a light emitting device comprising: a light source; a light incident surface on which light from the light source is incident; and a light guide having a light emission surface in which the emitted light has an optical shape such that the emitted light has predetermined optical characteristics. As a result of various studies, the inventor found that the optical shape of the light emitting surface is the first surface, the second surface,..., N (n ≧ 1) in the direction away from the optical axis of the optical shape. ) In order, and an angle θ _n (−90 ° ≦ θ _n ≦ 90 °) formed by the flat light incident surface and the nth surface satisfies θ _n ≦ θ _{n + 1.} By using the device, the light emitting device emits light more uniformly than the prior art.

  FIG. 1 is a top view of the best mode of the light guide according to the present invention as seen from the light exit surface side. FIG. 2 is a schematic cross-sectional view in the XX direction of FIG. 2 and 3, the path of light emitted from the light emitting surface of the light emitting diode and emitted through the light guide is indicated by a thin line.

  In the light emitting device according to this embodiment, a flat light guide 101 is disposed immediately above the light emitting diode 102 that is electrically and mechanically connected to the mounting substrate 103. Here, in the light guide 101, a surface facing the light emitting diode 102 is a light incident surface 101a, and a surface opposite to the light incident surface 101a is a light emitting surface 101b, that is, a light emission observation surface of the light emitting device. . In the light emitting device according to this embodiment, the light incident surface of the light guide and the light emitting surface of the light emitting diode are opposed to each other with a predetermined interval, but the present invention is not limited to such a configuration. For example, the light incident surface of the light guide and the light emitting surface of the light emitting diode may be brought into contact with each other. Alternatively, another light transmissive member such as an optical sheet or a filler made of a light transmissive resin may be interposed between the light incident surface of the light guide and the light emitting surface of the light emitting diode.

As shown in FIG. 2, the light emitting surface of the light guide according to this embodiment has a plurality of inclined surfaces in a direction away from the optical axis of the optical shape formed on the light emitting surface. FIG. 4 is a schematic diagram showing an enlarged cross section of the light guide according to this embodiment. Note that the nth surface forming the light emitting surface as shown in FIG. 2 is the outer inclined surface when viewed from the optical axis direction on the light emitting surface side among the inclined surfaces forming the protrusions. Say it. The number and size of the inclined surfaces forming the light emitting surface are variously selected depending on the size of the light emitting surface of the light emitting diode and the optical distance between the light emitting surface and the light incident surface of the light guide. The number and size of the inclined surfaces described in this embodiment are not limited. For example, as shown in FIG. 4, the light guide in this embodiment includes a first surface, a second surface, a third surface, a fourth surface, and a fifth surface in order from the optical axis side as a plurality of inclined surfaces. And has a sixth surface. Further, the first 'surface, the second' surface, the third 'surface, the fourth' surface in the direction away from the optical axis of the optical shape so as to be symmetric with respect to the optical axis with those surfaces, It has a 5 ′ surface and a 6 ′ surface in order (not shown for simplicity). Further, the angles θ _n (−90 ° ≦ θ _n ≦ 90 °) formed by these surfaces and the substantially flat light incident surface of the light guide in the optical axis direction are respectively θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ _5, and θ ₆ , θ ₁ <θ ₂ , θ ₂ <θ ₃ , θ ₃ <θ ₄ , θ ₄ <θ ₅ and θ ₅ <θ ₆ are satisfied. In addition, a plurality of angles may be equal among θ ₁ to θ ₆ . For example, θ ₂ = θ ₃ and θ ₄ = θ ₅ may be used. The same applies to the angle formed by the first 'surface to the sixth' surface and the substantially flat light incident surface of the light guide in the optical axis direction. The n-th surface is preferably connected to the n-th surface by the same surface or a plurality of continuous surfaces that are symmetric with respect to the n-th surface. Here, it is preferable that the same surface or a plurality of continuous surfaces are also symmetrical with respect to the optical axis.

  Further, the light emitting surface has a plurality of protrusions formed by the first surface to the sixth surface and the surfaces facing the first surface to the sixth surface, respectively. The section of the part is triangular. Further, the triangular apexes of the plurality of projecting portions are arranged on the substantially same plane on the light emitting surface side of the light guide so that the plane is substantially parallel to the light incident surface.

  Furthermore, as shown in FIG. 1, it is preferable that the light emission surface is formed by concentrically arranging a plurality of annular protrusions having first to sixth surfaces when viewed from the optical axis direction. . That is, it is preferable that the nth surface and the n′th surface that is symmetric with respect to the nth surface and the optical axis are the same surface and a curved surface. Thereby, it can be set as the light-emitting device which improved light distribution. In the present invention, it goes without saying that the arrangement of the protrusions viewed from the optical axis direction is not limited to the concentric shape, and various shapes such as an ellipse, a hexagon, and a polygon can be selected.

  Further, the light emitting surface is adjacent to any one of the first surface, the second surface,..., The nth (n ≧ 1) surface, and is substantially parallel to the flat light incident surface. It can also have a surface. For example, as shown in FIGS. 3 and 5, the light emitting surface of the light guide 201 is adjacent to the first surface and the second surface, and includes the same plane including each vertex of the protrusion 205 (and light incident). A plane substantially parallel to the plane). Thereby, the intensity of light incident from directly above the light source can be reduced, and a light emitting device having uniform luminance over the entire emission observation surface can be obtained.

  In this specification, the “optical axis” is the symmetrical center line of the optical shape formed on the light emitting surface of the light guide, and the optical axis in this embodiment is observed immediately above the light emitting surface of the light emitting diode. And the center line of the peak of the emitted light intensity. The light guide according to the present invention has an optical characteristic that reduces the relatively high luminance emitted from the light source by bending the path of the light beam in a direction away from the optical axis at the observation point directly above the light source. . In addition, the light guide according to the present invention has an optical characteristic such that the path of the light beam is bent substantially perpendicularly to the observation point at the observation point far from the optical axis.

  For example, when the light exit surface has an optical shape as shown in FIG. 3, the light incident on the light guide 201 from the light emitting diode 102 is first refracted by the light incident surface 201 a, and then the first surface from the first surface. The light exit surface 201b having four surfaces is refracted at different angles and is emitted from the light guide 201. Thereby, the light emission of the light emitting device is observed from the light emitting surface side with uniform luminance.

  Furthermore, the light emitting device according to the present invention preferably has a light diffuser that diffuses the light emitted from the light guide. Thus, a light emitting device that emits light more uniformly can be obtained. In addition, the light source in this invention can be variously selected, such as a light emitting diode, a laser diode, and an EL element. Hereinafter, each structure of this form is explained in full detail.

(Light guide)
The light guide in this embodiment refers to light from a light source incident from a part of the outer surface of the light guide by utilizing refraction due to its optical shape, and a desired light exit surface from a desired light exit surface. It can emit light in a shape. Therefore, the light guide has various shapes such as a meter needle, a flat plate that can be used as a planar light source such as a liquid crystal backlight, a wedge shape that gradually becomes thinner in a certain direction, depending on the desired shape of the light emitting surface of the light emitting device The shape can be as follows.

  The light guide has translucency in order to efficiently emit light from the light emitting diode or light obtained by wavelength conversion of the light from the light emitting surface. As a material of such a light guide, various materials excellent in light transmittance, such as transparent resin such as acrylic resin and epoxy resin, and glass, can be preferably cited. Using these as materials, light guides having various optical shapes as described above can be integrally formed by injection molding.

(Light diffuser)
Furthermore, it is preferable to provide a light diffuser that functions to make the luminance uniform by scattering light from the light guide on the light exit surface side of the light guide. Such a light diffuser has a high light transmittance and needs to diffuse light efficiently, and preferably has a transmittance of 50% or more, more preferably 70% or more. Examples of the material of the light diffuser include a transparent and highly heat-resistant polycarbonate film or polyester film coated with refractive fine particle resin beads or translucent inorganic fine particles, and further embossed. Due to the light scattering effect of the light scattering fine particles dispersed and contained in these members, the light incident on the light diffuser from the light guide is emitted with a more uniform light luminance distribution. Can do. Further, by making the surface of the light guide that comes into contact with the light diffuser into a concavo-convex shape, it is possible to prevent interference fringes that can be caused by the light diffuser sticking to the light guide. Moreover, it can also be set as the light diffuser which white pigment added and added. As a result, a light emitting device having a more uniform luminance can be obtained. Furthermore, an optical sheet such as a prism sheet can be placed in contact with or opposed to the light guide or the light diffuser to control optical characteristics such as light distribution of the light emitting device.

(Light emitting diode)
The light source in the present invention can be a light emitting diode, a laser diode, or an EL element. In particular, a light-emitting diode will be described as a light source in this embodiment. It is preferable that the light emitting diode in this embodiment can emit white mixed light. Examples of such light emitting diodes capable of emitting white light include various combinations of various light emitting diodes capable of emitting RGB, and light emitting diodes using semiconductor light emitting elements and phosphors. For example, it is possible to emit light with high luminance by using a gallium nitride compound semiconductor as a light emitting element capable of emitting blue light. In addition to the light emitting element, a light emitting diode in which a protective element such as a Zener diode or a capacitor for protecting the light emitting element from destruction due to overvoltage or an electronic element such as a resistor is mounted on a package can be provided.

  In addition, the light emitting diode in this embodiment preferably has a package having a recess. The electrode exposed in the recess and the LED chip disposed on the bottom of the recess are electrically connected by a conductive wire such as a gold wire or a conductive paste such as an Ag-containing epoxy resin. The inside of the package is sealed with a translucent resin such as an epoxy resin to form an SMD type light emitting diode.

(package)
The package in this embodiment has a conductor wiring that holds the LED chip and is electrically connected to the LED chip, and protects the LED chip from the external environment.
In particular, the package in this embodiment is preferably one in which an LED chip can be disposed on the bottom surface of a recess formed in the package. Epoxy resin, silicone resin, imide resin, acrylic resin, PBT (polybutylene terephthalate), liquid crystal polymer, aromatic It is suitably formed using various resins such as group nylon. In particular, in order to efficiently extract light from the LED chip with a package, it is preferable to appropriately mix calcium carbonate, aluminum oxide, or titanium oxide as a light diffusing agent in the various resins. Thereby, a white package with a high reflectance can be constituted.

  The package can be a ceramic package obtained by laminating and firing ceramic green sheets. Since the ceramic package is superior in heat resistance and light resistance as compared to a package made of a resin material, a high-output and highly reliable semiconductor light-emitting device can be obtained. In the ceramic package having a recess, the inner wall surface of the recess is preferably a reflecting surface made of a metal material having a high light reflectance. Thereby, since the light from the light emitting element is not absorbed by the ceramic, a light emitting diode having excellent light extraction efficiency can be obtained.

  The package is preferably filled with an LED chip and a translucent resin electrically connected to the lead electrode. Here, the translucent resin that covers the LED chip may contain a fluorescent material as necessary. Moreover, it is preferable that the package surface and the translucent resin on the light emission observation surface side are substantially flat in order to be easily brought into contact with the light incident surface of the light guide.

(Fluorescent substance)
The fluorescent material used in the present invention converts light from the light emitting diode, and it is more efficient to convert light from the light emitting diode to a longer wavelength. In the case where the light from the LED chip is high-energy short-wavelength visible light, perylene derivatives that are organic phosphors, ZnCdS: Cu, and YAG: Ce that is a kind of aluminum oxide phosphor (for example, YAlO ₃ : Ce). Y ₃ Al ₅ O ₁₂ : Ce, Y ₄ Al ₂ O ₉ : Ce, (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce, Y ₃ (Al _0.8 Ga _0.2 ) ₅ O ₁₂ : Ce, Tb _2.95 Ce _0.05 Al ₅ O ₁₂ , Y _2.90 Ce _0.05 Tb _0.05 Al ₅ O ₁₂ , Y _2.94 Ce _0.05 Pr _0.01 Al ₅ O ₁₂ , Y _2.90 Ce _0.05 Pr _0.05 Al ₅ O _12, etc.) and various suitable inorganic phosphors such as nitrogen-containing CaO—Al ₂ O ₃ —SiO ₂ activated by Eu and / or Cr Used for. In particular, when a YAG: Ce phosphor is used, depending on its content, the light from the blue LED and the yellow color that partially absorbs the light can be emitted, and the white color is relatively easy to trust. Since it can form with sufficient property, it is preferable. Similarly, when a nitrogen-containing CaO—Al ₂ O ₃ —SiO ₂ phosphor activated with Eu and / or Cr is used, light from the blue LED and a part of the light are absorbed depending on its content. Thus, a red color which is a complementary color can emit light, and a white color can be formed relatively easily and reliably.

(Mounting board)
The mounting substrate is for mounting a light emitting diode, and can be suitably configured by a glass epoxy substrate on which a conductive pattern made of copper foil or the like is formed, a metal body bonded with an insulating resin, or the like. Alternatively, a metal pattern made of aluminum or copper is provided with a conductive pattern through an insulating material, and heat dissipation can be improved. Moreover, it is preferable that a mounting board | substrate is arrange | positioned in a housing etc. via a heat radiating sheet.

  Examples according to the present invention will be described in detail below. Needless to say, the present invention is not limited to the following examples.

  The light emitting device according to this example used the light emitting diode shown in FIG. 2 as the light emitting diode. In order to electrically connect the LED chip and the electrode of the mounting substrate, the light emitting diode has a lead electrode exposed in the recess of the package and protruding from the outer surface of the package. In addition, the light emitting diode in this example is an SMD type light emitting diode having a light emitting surface on which light from an LED chip is mainly observed in a direction substantially perpendicular to the mounting surface with respect to the mounting substrate.

  The package in the present embodiment is molded into a shape having a recess by injection molding of a polyphthalamide resin on a lead frame obtained by punching a metal flat plate.

  The LED chip in this example emits blue light formed from an n-type gallium nitride semiconductor on a sapphire substrate, an indium gallium nitride / gallium nitride multiple quantum well structure in an active layer, and a p-type gallium nitride semiconductor double heterostructure. Use what is possible. This LED chip is die-bonded to the bottom of the package with an epoxy resin, and the p-type electrode and the n-type electrode provided on the n-type and p-type semiconductor surfaces of the LED chip are respectively exposed to the bottom surface of the recess by a gold wire. And wire bonding.

Further, a silicone resin containing a (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce phosphor is filled in the recess of the package to form an SMD light emitting diode capable of emitting white light.

  Next, a plurality of light emitting diodes are fixed and electrically connected by flow soldering on a mounting substrate made of aluminum in which a pattern to which the light emitting diodes can be connected is formed via an insulating material. This mounting board has a thin plate shape substantially equal to the size of the SMD type light emitting diode installation surface and the width of the light guide, and a plurality of SMD light emitting diodes are mounted at regular intervals when viewed from above. Yes.

  FIG. 2 is a schematic cross-sectional view of the light emitting device in the present example, and FIG. 4 is a schematic enlarged cross-sectional view of the light guide according to the present example. In FIG. 4, the intersection line between the nth surface (n = 1, 2, 3, 4, 5, 6) and the cut surface is extended and indicated by a dotted line, numbers 1 to 6 respectively. Is attached.

  The light guide body 101 shown in FIGS. 2 and 4 is formed in a substantially rectangular parallelepiped shape by injection molding using an acrylic resin as a material. One main surface of the light guide 101 is opposed to the light emitting surface of the SMD type light emitting diode 102 mounted on the mounting substrate 103, and serves as a light incident surface 103a. Further, the main surface opposite to the light incident surface 103a is a light emitting surface 103b, that is, a light emission observation surface.

The light guide 101 according to the present embodiment has a plurality of optical shapes as shown in FIG. 1, and the optical axis of each optical shape is aligned with the center line of the light emission peak of the light emitting diode 102. The optical shape in the present embodiment is a plurality of inclined surfaces and curved surfaces formed in a direction away from the optical axis of the light guide 101, that is, the first surface, the second surface, the third surface, and the fourth surface. , And a plurality of protrusions 105 having a fifth surface and a sixth surface in this order. The protrusions 105 are annular when viewed from the light exit surface direction, and the plurality of protrusions 105 are arranged in a concentric shape. The angles formed by these surfaces and the substantially flat light incident surface of the light guide in the optical axis direction are θ ₁ <θ ₂ , θ ₂ <θ ₃ , θ ₃ <θ ₄ , θ ₄ <θ ₅ and θ ₅ <θ ₆ is satisfied. In this example, θ ₁ = 30 °, θ ₂ = 45 °, θ ₃ = 45 °, θ ₄ = 60 °, θ ₅ = 60 °, and θ ₆ = 75 °.

  Further, a light diffusing body and a prism sheet are sequentially arranged on the light emitting surface 103b of the light guide body 101 to form a liquid crystal backlight. According to this embodiment, uniform and high-luminance light emission can be achieved as compared with a conventional liquid crystal backlight.

  FIG. 3 is a schematic cross-sectional view of the light emitting device according to the present example, and FIG. 5 is a schematic enlarged cross-sectional view of the light guide according to the present example. Further, in FIG. 5, the intersection line between the nth surface (n = 1, 2, 3, 4) and the cut surface is extended and indicated by a dotted line, and numbers 1 to 4 are attached respectively. is there.

  The light guide 201 according to the present embodiment has a plurality of optical shapes as shown in FIG. 5, and the optical axis of each optical shape coincides with the center line of the light emission peak of the light emitting diode 102. The optical shape in the present embodiment is a plurality of inclined surfaces and curved surfaces formed in a direction away from the optical axis of the light guide 201, that is, the first surface, the second surface, the third surface, and the fourth surface. It consists of a plurality of protrusions 205 having a surface in order. The protrusions 205 are annular when viewed from the light exit surface direction, and the plurality of protrusions 205 are arranged concentrically. In addition, the 1st surface in a present Example shall say the conical surface formed in rotational symmetry with respect to the optical axis. Similarly to the first embodiment, the second to fourth surfaces are outer surfaces as viewed from the optical axis direction on the light emitting surface 201b side, among the inclined surfaces forming the protrusions. Further, the surface adjacent to the first surface and the second surface is substantially parallel to the light incident surface 201a of the light guide and is substantially the same surface as the plane including the apex of the protruding portion. is there.

The angles formed by the first surface to the fourth surface and the substantially flat light incident surface of the light guide in the optical axis direction satisfy θ ₁ <θ ₂ , θ ₂ = θ ₃ <θ _4. Yes. Furthermore, in this example, θ ₁ = −30 °, θ ₂ = θ ₃ = 45 °, and θ ₄ = 60 °.

  A light diffusing body and a prism sheet are sequentially arranged on the light emitting surface 203b of the light guide 201 to form a liquid crystal backlight. The configuration is the same as that of the first embodiment except for the configuration as described above.

  The light emitting device according to the present embodiment can reduce the luminance on the optical axis as compared with the liquid crystal backlight of the first embodiment, and can emit light more uniformly and with high luminance.

  INDUSTRIAL APPLICABILITY The present invention can be used as a light emitting device used for a liquid crystal backlight, a switch push button, a nameplate, various display boards, and the like that require uniform and high luminance light emission.

FIG. 1 is a schematic top view showing an embodiment according to the present invention. FIG. 2 is a schematic sectional view showing an embodiment according to the present invention. FIG. 3 is a schematic sectional view showing an embodiment according to the present invention. FIG. 4 is a schematic sectional view showing an embodiment according to the present invention. FIG. 5 is a schematic sectional view showing an embodiment according to the present invention.

Explanation of symbols

101, 201 ... Light guides 101a, 201a ... Light incident surfaces 101b, 201b ... Light exit surface 102 ... Light source 103 ... Mounting substrate 104 ... Optical axes 105, 205 ... Protrusion

Claims (6)

A light emitting device comprising: a light source; and a light guide having a light incident surface on which light from the light source is incident and a light emitting surface having an optical shape having predetermined optical characteristics,
The optical shape of the light emitting surface has a first surface, a second surface,..., An nth (n ≧ 1) surface in order in a direction away from the optical axis of the optical shape,
An angle θ _n (−90 ° ≦ θ _n ≦ 90 °) formed by the light incident surface and the nth surface satisfies θ _n ≦ θ _{n + 1} . The light emitting device according to claim 1, wherein the light emitting surface has a protruding portion having a triangular cross section. The light emitting surface is formed by concentrically arranging protrusions having the first surface, the second surface,..., The nth (n ≧ 1) surface when viewed from the optical axis direction. The light emitting device according to claim 2. The light emission surface further includes a surface adjacent to any one of the first surface, the second surface,..., The nth (n ≧ 1) surface and substantially parallel to the light incident surface. The light emitting device according to claim 1. The light-emitting device according to claim 1, further comprising a light diffuser that diffuses light emitted from the light guide. The light-emitting device according to claim 1, wherein the light source is a light-emitting diode.

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