JP2006073202A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device causing extremely small color irregularity and capable of realizing full color. <P>SOLUTION: This light emitting device capable of emitting white-based light includes: a light source 100 having a laser diode 101 for emitting blue light and a laser diode 102 for emitting red light; a light guide plate 200 for transmitting light from the light source 100; a cylindrical lens 300 arranged between the light source 100 and the light guide plate 200 for diffusing the light from the light source; and a YAG phosphor 400 applied to a light extraction surface of the light guide plate 200. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting element used for a lighting fixture, a display, a liquid crystal backlight, and the like, and a light emitting device using a fluorescent material. In particular, the present invention relates to a light emitting device that emits white light using a laser diode and a fluorescent material.

  A light-emitting device using a light-emitting element emits light with a small color, high power efficiency, and vivid colors. In addition, since the light-emitting element is a semiconductor element, there is no fear of a broken ball. Further, it has excellent initial driving characteristics and is strong against vibration and repeated on / off lighting. Because of such excellent characteristics, light-emitting devices using light-emitting elements such as light-emitting diodes (LEDs) and laser diodes (LDs) are used as various light sources.

  Conventionally, a white light emission spectrum has been obtained by using a blue light emitting diode coated with a phosphor as a backlight. However, since the light output of the light emitting diode is based on spontaneous emission light in principle as compared with the laser diode, it is insufficient to obtain a sufficient light output. Further, when using a laser diode, it has been difficult to use the laser light output from the laser diode because of the danger to human eyes.

  In order to solve these problems, a distributed light source device using a semiconductor laser and a diffusion plate is conventionally known. (For example, refer to Patent Document 1). As shown in FIG. 15, in this distributed light source device, the light emitted from the semiconductor laser 700 is converged in the thickness direction of the diffusion plate 720 by the cylindrical lens 710 and introduced into the diffusion plate from the side of the diffusion plate 720. . Mirrors 740 are formed on the side and bottom surfaces of the diffuser plate 720 so that the introduced light is not scattered outside. The light introduced from the semiconductor laser 700 into the diffusion plate 720 is reflected by the mirror 740 or directly reaches the diffusion surface 730 and is converted into dispersed light.

JP-A-9-307174

  However, in the conventional light emitting device, although it is useful in that a light emitting device with high light output can be obtained by using a laser diode that can obtain high output light compared to a light emitting diode, Unlike the light-emitting diode, the light emitted from the semiconductor laser 700 is extremely straight, and the light is not uniformly dispersed inside the diffusion plate 720, and color unevenness occurs in the light emitted from the diffusion surface 730 to the outside. There is a problem. Further, since light from the semiconductor laser 700 is emitted to the outside through the diffusion plate 720 and the diffusion surface, it is not possible to make the color tone different from that of the light of the semiconductor laser 700, and to provide a light emitting device having various colors. There is a problem that you can not. Further, there is a problem that laser light output from the laser diode must be prevented from directly entering the human retina.

  In view of the above, an object of the present invention is to provide a light-emitting device capable of realizing full color with high luminance and extremely small color unevenness.

  In order to solve the above-mentioned problems, the present inventor has intensively studied, and as a result, the present invention has been completed.

  The present invention is a light emitting device having a light source and a light guide plate that transmits light from the light source, wherein the light source has a first light emitting element and an emission peak wavelength of the first light emitting element. A second light emitting element having an emission peak wavelength on the long wavelength side, wherein the light guide plate absorbs at least part of light from the first light emitting element and emits light of different wavelengths And a light emitting device in which at least light from the second light emitting element and light from the fluorescent material are mixed and emitted to the outside. Here, “having a fluorescent material” means that the fluorescent material is contained in the light guide plate, a coating containing the fluorescent material is attached to the light guide plate, and the fluorescent material is introduced through an adhesive or the like. It means that it is attached to the surface.

  The light emitting device may be a device in which light from the first light emitting element is further mixed and emitted to the outside.

  Either of the first light emitting element and the second light emitting element is preferably a laser diode.

  As the fluorescent material, one having an emission peak wavelength on the longer wavelength side than the emission peak wavelength of the first light emitting element can be used.

  As the fluorescent material, those having an emission peak wavelength between the emission peak wavelength of the first light emitting element and the emission peak wavelength of the second light emitting element can be used.

  As the fluorescent material, quantum dots can be used in addition to the fluorescent material.

  As the first light emitting element, a visible light can be used.

  As the first light emitting element, one having an emission peak wavelength between 380 nm and 495 nm can be used. In this specification, light having a wavelength of 380 nm or more is regarded as visible light.

  As the first light emitting element, an ultraviolet light can be used. For example, the ultraviolet light having an emission peak wavelength between 300 nm and less than 380 nm can be used. In this specification, light of less than 380 nm is ultraviolet light.

  The light source may include a plurality of the first light emitting elements and the second light emitting elements. In addition to arranging a plurality of combinations of the first light emitting element and the second light emitting element, a plurality of the first light emitting elements are arranged, and the second light emitting element is interposed between them. Various combinations can be used, such as arranging two, a plurality of first light emitting elements, and two second light emitting elements at both ends.

  As the light guide plate, one containing the fluorescent material can be used.

  The present invention is a light emitting device including a light source, a light guide plate that transmits light from the light source, and a light diffusion member provided between the light source and the light guide plate, wherein the light source includes a laser diode. The light guide plate includes a fluorescent material that absorbs at least a part of the light from the laser diode and emits light of a different wavelength, and at least one of the light from the laser diode and the light from the fluorescent material The present invention relates to a light emitting device in which such light is emitted to the outside.

  As the light guide plate, one containing a diffusing material may be used.

  The light guide plate is preferably coated with the fluorescent material on the surface of the light extraction surface.

  It is preferable that the light guide plate has the fluorescent material disposed on a surface side from which light is extracted.

  In the light guide plate, the fluorescent material may be disposed on at least a part near a surface different from a surface from which light is extracted.

  It is preferable that the light guide plate has an ultraviolet absorber disposed inside or near the outside of the surface from which light is extracted.

  The light guide plate preferably disperses the diffusing material substantially uniformly.

  The light emitting device preferably includes a light diffusing member between the light source and the light guide plate.

  Since the present invention is configured as described above, the following effects can be obtained.

  The present invention is a light emitting device having a light source and a light guide plate that transmits light from the light source, wherein the light source has a first light emitting element and an emission peak wavelength of the first light emitting element. A second light emitting element having an emission peak wavelength on the long wavelength side, wherein the light guide plate absorbs at least part of light from the first light emitting element and emits light of different wavelengths And a light emitting device in which at least light from the second light emitting element and light from the fluorescent material are mixed and emitted to the outside. In general, when the amount of electric power input to the first light emitting element is increased, the light emitted from the first light emitting element tends to shift to the short wavelength side. At this time, when light from the first light-emitting element and light from the second light-emitting element are mixed, color misregistration occurs. On the other hand, in the present invention, when a fluorescent material is excited by light from the first light emitting element, light having a substantially constant chromaticity can be obtained. A light emitting device with a small color shift can be provided by mixing light of a certain chromaticity emitted from the fluorescent material and light from the second light emitting element. In particular, the first light emitting element preferably has an emission peak wavelength in the ultraviolet region. Accordingly, it is difficult to visually perceive the color shift of the first light emitting element, and a light emitting device with a small color shift can be provided.

  The light emitting device may be a device in which light from the first light emitting element is further mixed and emitted to the outside. Thereby, the color tone range of the light emitted from the light emitting device can be expanded.

  Either of the first light emitting element and the second light emitting element is preferably a laser diode. As a result, a light emitting device having a higher emission intensity than when a light emitting diode is used can be provided.

  As the fluorescent material, one having an emission peak wavelength on the longer wavelength side than the emission peak wavelength of the first light emitting element can be used. Thus, a light emitting device with high energy conversion efficiency can be provided.

  As the fluorescent material, those having an emission peak wavelength between the emission peak wavelength of the first light emitting element and the emission peak wavelength of the second light emitting element can be used. For example, by combining a first light emitting element that emits blue light, a fluorescent material that emits green light, and a second light emitting element that emits red light, a three-wavelength light emitting device that emits white light can be provided. . In addition, a light-emitting device that emits white light can be provided by combining a first light-emitting element that emits ultraviolet light, a fluorescent material that emits blue-green light, and a second light-emitting element that emits red light. As a result, a fluorescent material having a high wavelength conversion efficiency can be combined, so that a light emitting device with high emission intensity and a wide color tone range can be provided.

  Quantum dots can be used as the fluorescent material. Quantum dots (nanoparticles) have the property that the emission wavelength varies depending on the incident wavelength due to the size of the particles, even though they are the same substance. Therefore, since the color tone can be converted only by changing the particle size, it is extremely useful.

  As the first light emitting element, a visible light can be used. Since the light emitted from the first light emitting element can be visually recognized, the light from the first light emitting element can be used effectively.

  As the first light emitting element, one having an emission peak wavelength between 380 nm and 495 nm can be used. This is because the fluorescent material is excited by light from the first light-emitting element, so that it is preferable to have high energy, and since it is visible light, it can contribute to the emission color.

  As the first light emitting element, an ultraviolet light can be used. Since the light emitting element tends to shift to the short wavelength side when the input power amount is increased, if the light emitted from the light emitting element is visible light, color deviation may occur in the light emitted from the light emitting device. Therefore, a light-emitting device with small color shift can be provided by using ultraviolet light that cannot be visually recognized. For example, a peak wavelength of around 370 nm or 375 nm can be used.

  The light source may include a plurality of the first light emitting elements and the second light emitting elements. From the visibility characteristic, it is possible to reduce color variation by increasing the light emission intensity in a region with relatively low visibility. In addition, color unevenness on the same surface can be reduced.

  As the light guide plate, one containing the fluorescent material can be used. This eliminates the step of depositing the fluorescent material on the light guide plate. In addition, the film containing the fluorescent material can be prevented from being peeled off from the light guide plate. Further, since the fluorescent material can be uniformly contained in the light guide plate, uneven color can be prevented.

  The fluorescent material has a light emission peak wavelength between a light emission peak wavelength of the first light emitting element and a light emission peak wavelength of the second light emitting element, and the light guide plate contains the fluorescent material. You can also Thereby, when the light emitted from the second light emitting element is irradiated onto the fluorescent material, most of the light is reflected. Thereby, the fluorescent substance functions as a light diffusing material, and the light diffusing effect is enhanced. Therefore, a light emitting device that emits light uniformly can be provided by uniformly dispersing the fluorescent material in the light guide plate.

  The present invention is a light emitting device including a light source, a light guide plate that transmits light from the light source, and a light diffusion member provided between the light source and the light guide plate, wherein the light source includes a laser diode. The light guide plate includes a fluorescent material that absorbs at least a part of the light from the laser diode and emits light of a different wavelength, and at least one of the light from the laser diode and the light from the fluorescent material The present invention relates to a light emitting device in which such light is emitted to the outside. When a light-emitting device is used as illumination light, a laser diode has high light condensing properties. Therefore, it is very dangerous if the laser light directly enters the eyes, and thus it is necessary to use dispersed light. Therefore, a light diffusion member is disposed between the laser diode and the light guide plate to disperse the laser light. Moreover, the light emitted from the light guide plate can be made uniform by dispersing the laser light.

  As the light guide plate, one containing a diffusing material may be used. Thereby, the light emitted from the light guide plate can be made uniform.

  The light guide plate is preferably coated with the fluorescent material on the surface from which light is extracted. This facilitates the manufacturing process because the fluorescent material is applied after the light guide plate is molded. Moreover, since a fluorescent substance is not mixed in the light guide plate, heat can be applied in forming the light guide plate, and a stronger light guide plate can be formed.

  It is preferable that the light guide plate has the fluorescent material disposed on a surface side from which light is extracted. Thereby, the part which wavelength-converts with a fluorescent material and the part which does not perform wavelength conversion can be divided.

  In the light guide plate, the fluorescent material may be disposed on at least a part near a surface different from a surface from which light is extracted. If a diffusion material is mixed in the light guide plate, the light emitted from the fluorescent material can be diffused inside the light guide plate, and the light from the second light emitting element and the light from the fluorescent material are mixed uniformly. Can be done. In addition, a light emitting device that enhances the light diffusion effect from the first light emitting element by providing a reflecting plate on a different surface and reflects light from the fluorescent material by the reflecting plate to provide more uniform light emission can do.

  It is preferable that the light guide plate has an ultraviolet absorber disposed inside or near the outside of the surface from which light is extracted. Since ultraviolet rays may be harmful to the human body, a light emitting device that emits less ultraviolet rays can be provided by arranging a member that absorbs ultraviolet rays.

  The light guide plate may disperse the diffusing material substantially uniformly. As a result, light from the light source can be dispersed, and light can be extracted uniformly from the light extraction surface.

  The light emitting device preferably includes a light diffusing member between the light source and the light guide plate. As a result, the light from the light source can be dispersed before the light enters the light guide plate, and the light can be dispersed even by the fluorescent material disposed inside the light guide plate, so that the light can be uniformly extracted from the light guide plate. it can.

  Hereinafter, a light-emitting device and a manufacturing method thereof according to the present invention will be described with reference to embodiments and examples. However, the present invention is not limited to this embodiment and example.

<First Embodiment>
FIG. 1 is a schematic perspective view showing a light emitting device according to the present invention. FIG. 2 is a schematic cross-sectional view showing a light emitting device according to the present invention. FIG. 2 is a schematic cross-sectional view taken along the line II of FIG.

<Light emitting device>
The light emitting device according to the first embodiment includes a light source 100, a light guide plate 200 that transmits light from the light source 100, and a light diffusion member 300 provided between the light source 100 and the light guide plate 200. The light source 100 includes a first light emitting element 101 and a second light emitting element 102. The second light emitting element 102 has a light emission peak wavelength on the longer wavelength side than the light emission peak wavelength of the first light emitting element 101. The light guide plate 200 has, on the light extraction surface 200a, a fluorescent material 400 that absorbs part of the light from the first light emitting element 101 and emits light of different wavelengths. Here, a coating containing the fluorescent material 400 is attached to the light extraction surface 200 a of the light guide plate 200. The inside of the light guide plate 200 is made of a translucent member, and the bottom surface 200b and the side surface 200c are provided with reflecting members. The light extraction surface 200a of the light guide plate 200 is configured to emit light reflected and scattered inside the light guide plate 200 to the outside. The light diffusing member 300 diffuses light from the light source 100 and functions as a condenser lens to efficiently guide light into the light guide plate 200. The fluorescent material 400 absorbs part of the light from the first light emitting element 101 and emits light of different wavelengths. On the other hand, since the fluorescent material 400 has a light emission peak wavelength shorter than the light emission peak wavelength of the second light emitting element 102, the light emitted from the second light emitting element 102 is almost free of the fluorescent material 400. Wavelength conversion is not performed. Therefore, the light from the second light emitting element 102 is emitted to the outside from the light extraction surface 200 a without being wavelength-converted by the fluorescent material 400.

  The light emitting device emits light by the following operation.

  Light from the light source 100 having the first light emitting element 101 and the second light emitting element 102 passes through the light diffusing member 300 and enters the inside from the side surface portion of the light guide plate 200. At this time, the light emitted from the light source spreads by the light diffusing action, but when the light enters the light diffusing member 300, the light is condensed by the condensing lens of the light diffusing member 300, and the light from the light source is efficiently guided. It is incident on the side surface portion of 200. The light incident on the inside of the light guide plate 200 is reflected by the bottom surface 200b and the side surface 200c of the light guide plate 200 and is emitted to the outside from the light extraction surface 200a. The light extraction surface 200a of the light guide plate 200 is coated with a coating containing the fluorescent material 400, and the light from the first light emitting element 101 is converted in wavelength to emit light of different wavelengths to the outside. . At this time, the light emitted from the light extraction surface 200 a is a mixed color light of the light from the fluorescent material 400 and the light from the second light emitting element 102. For example, in the case where the first light emitting element 101 is ultraviolet light, mixed color light (for example, blue-green light) from the fluorescent material 400 and light from the second light emitting element 102 (for example, red light) ( White light) is emitted from the light extraction surface 200 a of the light guide plate 200. On the other hand, when the first light emitting element 101 is visible light (for example, blue light), light from the fluorescent material 400 (for example, green light) and light from the second light emitting element 102 (for example, red light) Light) is emitted from the light extraction surface 200 a of the light guide plate 200. This is because not all of the light from the first light-emitting element 101 is absorbed by the fluorescent material 400, but part of the light from the first light-emitting element 101 is not absorbed by the fluorescent material 400 and is in the light guide plate 200 or the like. And is released to the outside.

  Hereinafter, each component will be described in detail.

<Light source>
The light source 100 includes a first light emitting element 101 and a second light emitting element 102. As the first light emitting element 101 and the second light emitting element 102, a light emitting diode (LED) or a laser diode (LD) can be used. In particular, when manufacturing a high-power light-emitting device, it is preferable to use a high-power laser diode rather than a light-emitting diode. Laser diodes are more likely to be incident on the light guide plate 200 because they have higher light condensing properties than light emitting diodes and are more straight ahead. On the other hand, when high-output light is incident on the light guide plate 200, the incident site may be damaged. Therefore, the light diffusion member 300 is used to diffuse the laser light to suppress damage to the light guide plate 200.

  The light source 100 may include a plurality of first light emitting elements 101 and second light emitting elements 102. In addition to arranging a plurality of combinations of a combination of the first light emitting element 101 and the second light emitting element 102, three first light emitting elements 101 are arranged between the first light emitting element 101 and the second light emitting element 102. Various combinations such as arranging two light emitting elements 102, arranging a plurality of first light emitting elements 101, and arranging two second light emitting elements 102 at both ends can be used. As a result, the light of the low visibility is compensated.

  As the first light-emitting element, a laser diode mainly emitting ultraviolet light, blue-violet light, or blue light is used. This is because the wavelength of the fluorescent material 400 is more efficiently converted. As the second light emitting element, a yellow-red light emitting laser diode and a red light emitting laser diode are mainly used. It is preferable to use a material having a complementary color relationship with the emission color of the fluorescent material 400. However, when a green or yellow-green laser diode is developed, a combination thereof can be used.

  It is preferable to provide the first light emitting element 101 and the second light emitting element 102 in the light source 100 in the vertical direction with respect to the plane of the light guide plate 200. This is because the light from the fluorescent material 400 that has been wavelength-converted by the first light emitting element 101 inside the light guide plate 200 and the light from the second light emitting element 102 are mixed and the surface light is uniformly emitted.

  A plurality of light sources 100 are preferably provided on the left and right along the plane of the light guide plate 200. In this case, as described above, it is preferable that the first light-emitting element 101 and the second light-emitting element 102 are provided on the left and right in a plurality of sets as one set. Since the laser diode has strong straightness and it is difficult to uniformly emit the entire light emitting surface of the light guide plate 200, it is preferable to provide a plurality of light sources 100 separated by a predetermined interval. The number of light emitting elements to be used is not particularly limited.

<Light emitting element>
As described above, the light emitting elements 101 and 102 used in the light source 100 are light emitting diodes or laser diodes. Laser diodes are preferred because they can emit high power light. Both the first light-emitting element 101 and the second light-emitting element 102 are preferably laser diodes, but a combination in which a laser diode is used for the first light-emitting element 101 and a light-emitting diode is used for the second light-emitting element 102 is also possible. is there. As a result, a light-emitting device with high output and high color rendering can be provided. Further, a light-emitting diode can be used for the first light-emitting element 101, and a laser diode can be used for the second light-emitting element 102.

  As the first light-emitting element 101, one that is visible light can also be used. This is because the light from the first light emitting element 101 can also be used effectively. In particular, the first light-emitting element 101 having an emission peak wavelength between 380 nm and 495 nm can be used. Among visible light wavelengths, those having a light emission peak wavelength on the short wavelength side have higher energy than those having a light emission peak wavelength on the long wavelength side, so that the fluorescent material 400 can be illuminated more efficiently. In this specification, light having a wavelength of 380 nm or more is defined as visible light.

  As the first light-emitting element 101, one that is ultraviolet light can also be used. In general, the emission peak wavelength of a light emitting element shifts to the short wavelength side as the input current increases, and therefore, when a visible light emitting element is used, color shift may occur. However, when an ultraviolet light emitting element is used, the deviation of the emission peak wavelength accompanying the increase in the input current to the light emitting element does not affect the emission color, so that the color deviation can be reduced. Note that ultraviolet light having an emission peak wavelength between 300 nm and less than 380 nm can be used. In this specification, light of less than 380 nm is ultraviolet light.

  The second light emitting element 102 has a light emission peak wavelength on the longer wavelength side than the light emission peak wavelength of the first light emitting element 101. This is because a combination of the light from the fluorescent material 400 and the light from the second light-emitting element 102 can provide a high-output light-emitting device with little color misregistration.

(Light emitting diode)
The light emitting diodes 101 and 102 are semiconductor light emitting diodes having an emission spectrum that can excite the fluorescent material 400 efficiently (that is, semiconductor light emitting diodes having a light emitting layer that emits light of an emission spectrum that can excite the fluorescent material efficiently). Is preferred. Examples of the material of such a semiconductor light emitting diode include various semiconductors such as BN, SiC, ZnSe, GaN, InGaN, InAlGaN, AlGaN, BAlGaN, and BInAlGaN. Further, these elements can contain Si, Zn, or the like as an impurity element to be a light emission center. In particular, a nitride semiconductor (eg, a nitride semiconductor containing Al or Ga, a nitride containing In or Ga, or the like) as a material of a light emitting layer capable of efficiently emitting a short wavelength of visible light from the ultraviolet region that can excite the phosphor 400 efficiently. sEMICONDUCTOR as _{in X Al Y Ga 1-X} -Y N, 0 <X <1,0 <Y <1, X + Y ≦ 1) can be mentioned as more preferable.

  Further, as a semiconductor structure, a homostructure having a MIS junction, a PIN junction, a pn junction, or the like, a heterostructure, or a double hetero configuration is preferably exemplified. Various emission wavelengths can be selected depending on the semiconductor layer material and the mixed crystal ratio. Further, the output can be further improved by adopting a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed in a thin film that produces a quantum effect.

  When a nitride semiconductor is used, a material such as sapphire, spinel, SiC, Si, ZnO, GaAs, or GaN is preferably used for the semiconductor substrate. In order to form a nitride semiconductor with good crystallinity with high productivity, it is preferable to use a sapphire substrate. A nitride semiconductor can be formed on the sapphire substrate by HVPE method, MOCVD method or the like. A buffer layer made of GaN, AlN, GaAIN or the like is grown at a low temperature on the sapphire substrate to form a non-single crystal, and a nitride semiconductor having a pn junction is formed thereon.

  An example of a light emitting diode capable of efficiently emitting light in the ultraviolet region having a pn junction using this nitride semiconductor is as follows.

First, on the buffer layer, SiO ₂ is formed in a stripe shape substantially perpendicular to the orientation flat surface of the sapphire substrate. GaN is grown on the stripes using EHV (Epitaxial Lateral Over Grows GaN) using the HVPE method. Subsequently, a first contact layer formed of n-type gallium nitride, a first cladding layer formed of n-type aluminum nitride / gallium, a well layer of indium nitride / aluminum / gallium, and aluminum nitride / gallium are formed by MOCVD. An active layer having a multiple quantum well structure in which a plurality of barrier layers are stacked, a second cladding layer formed of p-type aluminum nitride / gallium nitride, and a second contact layer formed of p-type gallium nitride are sequentially stacked.

  Further, the following may be performed without using ELOG growth.

  For example, an n-type GaN layer in which Si is undoped, an n-type contact layer made of n-type GaN in which Si is doped, an undoped GaN layer, and a light emitting layer having a multiple quantum well structure (through a GaN buffer layer on the sapphire substrate 1 ( GaN barrier layer / InGaN well layer quantum well structure), Mg-doped p-type GaN p-clad layer, and Mg-doped p-type GaN p-type contact layer. . And an electrode is formed as follows.

  The p ohmic electrode is formed on almost the entire surface of the p-type contact layer, and the p pad electrode is formed on a part of the p ohmic electrode.

  The n-electrode is formed in the exposed portion by removing the undoped GaN layer from the p-type contact layer by etching to expose a part of the n-type contact layer.

  In the present embodiment, the light emitting layer having a multiple quantum well structure is used. However, the present invention is not limited to this, and for example, a single quantum well structure using InGaN may be used. Alternatively, GaN doped with n-type and p-type impurities such as Zn may be used.

  The light emitting layers of the light emitting diodes 101 and 102 can change the main light emission peak in the range of 420 nm to 490 nm by changing the In content. The emission wavelength is not limited to the above range, and those having an emission wavelength of 360 to 550 nm can be used.

  Thus, a semiconductor light emitting diode having a double hetero structure is formed on the substrate. In the present invention, a semiconductor laser diode in which the active layer is formed in a ridge stripe shape and sandwiched between guide layers and a resonator end face is provided may be used.

  Nitride semiconductors exhibit n-type conductivity without being doped with impurities. When forming a desired n-type nitride semiconductor, for example, to improve luminous efficiency, it is preferable to appropriately introduce Si, Ge, Se, Te, C, etc. as an n-type dopant. On the other hand, when forming a p-type nitride semiconductor, it is preferable to dope p-type dopants such as Zn, Mg, Be, Ca, Sr, and Ba. Since nitride semiconductors are not easily converted to p-type by simply doping with a p-type dopant, it is preferable to reduce resistance by heating in a furnace or plasma irradiation after introducing the p-type dopant. When the sapphire substrate is not used, the contact layer is exposed by etching from the p-type side to the surface of the first contact layer. A light emitting diode made of a nitride semiconductor can be formed by forming an electrode on each contact layer and then cutting the semiconductor wafer into chips.

  In order to form the light emitting device with high productivity, it is preferable to use a light-transmitting sealing member. In particular, a translucent resin is preferable because the fluorescent material 11 is mixed and sealed. In this case, considering the emission wavelength from the phosphor and the deterioration of the translucent resin, the light emitting diode has an emission spectrum in the ultraviolet region, and the main emission wavelength is from 360 nm to 420 nm, or from 450 nm to 470 nm. Can also be used.

Here, in the semiconductor light emitting diode, the sheet resistance of the n-type contact layer formed at an impurity concentration of 10 ¹⁷ to 10 ²⁰ / cm ³ and the sheet resistance of the light-transmitting p electrode have a relationship of Rp ≧ Rn. It is preferable that the adjustment is performed. The n-type contact layer is preferably formed to a film thickness of, for example, 3 to 10 μm, more preferably 4 to 6 μm, and the sheet resistance is estimated to be 10 to 15Ω / □, so that Rp at this time is the sheet resistance value. It is good to form in a thin film so that it may have the above sheet resistance values. The translucent p-electrode may be formed of a thin film having a thickness of 150 μm or less. Moreover, ITO other than a metal and ZnO can also be used for a p electrode. Here, instead of the translucent p-electrode, an electrode having a plurality of light extraction openings such as a mesh electrode may be used.

  Further, when the translucent p-electrode is formed of a multilayer film or alloy composed of one kind selected from the group of gold and platinum group elements and at least one other element, it is contained. When the sheet resistance of the translucent p-electrode is adjusted by the content of the gold or platinum group element, stability and reproducibility are improved. Since gold or metal element has a high absorption coefficient in the wavelength region of the semiconductor light emitting diode used in the present invention, the smaller the amount of gold or platinum group element contained in the translucent p-electrode, the better the transparency. In the conventional semiconductor light emitting diode, the relationship of sheet resistance is Rp ≦ Rn. However, in the present invention, Rp ≧ Rn, and therefore the translucent p-electrode is formed in a thin film as compared with the conventional one. However, thinning can be easily realized by reducing the content of the gold or platinum group element.

  As described above, in the semiconductor light emitting diode, it is preferable that the sheet resistance RnΩ / □ of the n-type contact layer and the sheet resistance RpΩ / □ of the translucent p electrode satisfy the relationship of Rp ≧ Rn. It is difficult to measure Rn after it is formed as a semiconductor light emitting diode, and it is practically impossible to know the relationship between Rp and Rn, but what is the relationship between Rp and Rn from the state of the light intensity distribution during light emission. It is possible to know if they are related.

  Further, in the light emitting diode, when the translucent p electrode and the n-type contact layer have a relationship of Rp ≧ Rn, a p-side pedestal electrode having an extended conductive portion in contact with the translucent p electrode is provided. The external quantum efficiency can be further improved. There is no limitation on the shape and direction of the extended conductive portion, and when the extended conductive portion is on the satellite, it is preferable because the area for blocking light is reduced, but a mesh shape may be used. Further, the shape may be a curved shape, a lattice shape, a branch shape, or a hook shape in addition to the straight shape. At this time, since the light shielding effect increases in proportion to the total area of the p-side pedestal electrode, it is preferable to design the line width and length of the extended conductive portion so that the light shielding effect does not exceed the light emission enhancing effect.

(Laser diode)
As a nitride semiconductor used for the light-emitting elements 101 and 102, GaN, AlN, InN, or a gallium nitride-based compound semiconductor that is a mixed crystal thereof (In _x Al _y Ga _1-xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1). In addition, a part of the gallium nitride compound semiconductor is substituted with B and P.

In a nitride semiconductor laser, an active layer made of In _x Ga _1-x N (0 ≦ x <1) is formed on an n-type Al _y Ga _1-y N (0 ≦ y <1) layer (each layer) on a GaN substrate. Each of which has a different y value) and a p-type Al _z Ga _1-z N (0 ≦ z <1) layer (a different z value for each layer), forming a so-called double heterostructure Has been.

The active layer is an In _x1 Al _y1 Ga _1-x1-y1 N well layer (0 ≦ x ₁ ≦ 1, 0 ≦ y ₁ ≦ 1, 0 ≦ x ₁ + y ₁ ≦ 1) and In _x2 Al _y2 Ga _{1-x2 -Y2} N barrier layer (0 ≦ x ₂ ≦ 1, 0 ≦ y ₁ ≦ 1, 0 ≦ x ₁ + y ₁ ≦ 1, x ₁ > x ₂ ) is an appropriate number of times in the order of barrier layer-well layer-barrier layer In this case, both ends of the active layer are barrier layers. The well layer is formed undoped. On the other hand, except for the final barrier layer adjacent to the p-type electron confinement layer, all barrier layers are doped with n-type impurities such as Si and Sn, and the final barrier layer is grown undoped. In the final barrier layer, p-type impurities such as Mg are diffused from the adjacent p-type nitride semiconductor layer.

  Since the barrier layer except the final barrier layer is doped with n-type impurities, the initial electron concentration in the active layer is increased, the electron injection efficiency into the well layer is increased, and the laser emission efficiency is improved. On the other hand, since the final barrier layer is closest to the p-type layer, it does not contribute to electron injection into the well layer. Therefore, the hole injection efficiency into the well layer can be increased by not doping the final barrier layer with the n-type impurity, but rather by substantially doping the p-type impurity by diffusion from the p-type layer. In addition, by not doping the final barrier layer with n-type impurities, it is possible to prevent different types of impurities from being mixed in the barrier layer and lowering the carrier mobility.

The details of the structure of the nitride semiconductor laser will be described below. As the substrate, GaN is preferably used, but a heterogeneous substrate different from the nitride semiconductor may be used. Examples of the heterogeneous substrate include, for example, sapphire, spinel (including an insulating substrate such as MgA1 ₂ O ₄ , SiC (including 6H, 4H, and 3C) having any one of the C-plane, R-plane, and A-plane. It has been conventionally known that a nitride semiconductor such as ZnS, ZnO, GaAs, Si, and an oxide substrate lattice-matched with a nitride semiconductor can be grown, and a substrate material different from the nitride semiconductor can be used. Preferred examples of the heterogeneous substrate include sapphire and spinel, and the heterogeneous substrate may be off-angled, and in this case, if an off-angled stepped substrate is used, the underlying layer made of gallium nitride has good crystallinity. Furthermore, in the case of using a heterogeneous substrate, after growing a nitride semiconductor serving as a base layer before forming the element structure on the heterogeneous substrate, the heterogeneous substrate is used. Is removed by a method such as polishing, it may form a device structure as a single substrate of nitride semiconductor, also after the device structure formed may be a method of removing foreign substrate.

  In the case of using a heterogeneous substrate, if the element structure is formed via a base layer made of a buffer layer (low temperature growth layer) and a nitride semiconductor (preferably GaN), the growth of the nitride semiconductor becomes good. In addition, when a nitride semiconductor grown by ELOG (Epitaxially Laterally Overgrowth) is used as a base layer (growth substrate) provided on a different substrate, a growth substrate having good crystallinity can be obtained. As a specific example of the ELOG growth layer, a nitride semiconductor layer is grown on a heterogeneous substrate, a mask region formed by providing a protective film on which the nitride semiconductor growth is difficult, and a nitride semiconductor are formed. A non-mask region to be grown is provided in a stripe shape, and a nitride semiconductor is grown from the non-mask region, so that the growth in the lateral direction is achieved in addition to the growth in the film thickness direction. There is also a layer formed by growing a nitride semiconductor. In another form, the nitride semiconductor layer grown on the different kind of substrate may be provided with an opening, and the film may be formed by lateral growth from the side of the opening.

  An n-type contact layer, a crack prevention layer, an n-type cladding layer, and an n-type light guide layer, which are n-type nitride semiconductor layers, are formed on the substrate via a buffer layer. Other layers other than the n-type cladding layer may be omitted depending on the element. The n-type nitride semiconductor layer needs to have a wider band gap than that of the active layer at least in a portion in contact with the active layer, and therefore, preferably has a composition containing Al. Each layer may be grown while doping with n-type impurities to be n-type, or may be grown undoped to be n-type.

An active layer is formed on the n-type nitride semiconductor layer. As described above, the active layer is an In _x1 Al _y1 Ga _1-x1-y1 N well layer (0 ≦ x ₁ ≦ 1, 0 ≦ y ₁ ≦ 1, 0 ≦ x ₁ + y ₁ ≦ 1) and In _x2 Al _y2. Ga _1-x2-y2 N barrier layers (0 ≦ x ₂ ≦ 1, 0 ≦ y ₁ ≦ 1, 0 ≦ x ₁ + y ₁ ≦ 1, x ₁ > x ₂ ) were alternately and repeatedly stacked an appropriate number of times. It has an MQW structure, and both ends of the active layer are barrier layers. The well layer is undoped, and all the barrier layers except the final barrier layer are preferably doped with n-type impurities such as Si and Sn at a concentration of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ cm ^−3. Is formed.

The final barrier layer is formed undoped and contains p-type impurities such as Mg by 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^{−3 due} to diffusion from the p-type electron confinement layer to be grown next. When the final barrier layer is grown, it may be grown while doping a p-type impurity such as Mg at a concentration of 1 × 10 ¹⁹ cm ⁻³ or less. The final barrier layer is formed thicker than the other barrier layers in order to suppress the influence of decomposition by gas etching when the p-type electron confinement layer is grown next. The suitable thickness of the final barrier layer varies depending on the growth conditions of the p-type electron confinement layer. For example, the thickness is preferably 1.1 to 10 times, more preferably 1.1 to 5 times that of the other barrier layers. To grow. Thus, the final barrier layer serves as a protective film that prevents the decomposition of the active layer containing In.

  On the final barrier layer, as a p-type nitride semiconductor layer, a p-type electron confinement layer, a p-type light guide layer, a p-type cladding layer, and a p-type contact layer are formed. Other layers other than the p-type cladding layer may be omitted depending on the element. The p-type nitride semiconductor layer needs to have a wider band gap than that of the active layer at least in a portion in contact with the active layer, and therefore, it is preferably a composition containing Al. Each layer may be grown while doping with p-type impurities to be p-type, or p-type impurities may be diffused from other adjacent layers to be p-type.

The p-type electron confinement layer is made of a p-type nitride semiconductor having an Al mixed crystal ratio higher than that of the p-type cladding layer, and preferably has a composition of Al _x Ga _1-x N (0.1 <x <0.5). Have Further, a p-type impurity such as Mg is doped at a high concentration, preferably 5 × 10 ¹⁷ to 1 × 10 ¹⁹ cm ⁻³ . Thereby, the p-type electron confinement layer can effectively confine electrons in the active layer, and lowers the laser threshold. Further, the p-type electron confinement layer may be grown as a thin film of about 30 to 200 mm, and if it is a thin film, it can be grown at a lower temperature than the p-type light guide layer and the p-type optical cladding layer. Therefore, by forming the p-type electron confinement layer, decomposition of the active layer containing In can be suppressed as compared with the case where the p-type light guide layer or the like is formed directly on the active layer.

The p-type electron confinement layer plays a role of supplying p-type impurities to the final barrier layer grown by undoping by diffusion, and both cooperate to protect the active layer from decomposition and to the active layer. It plays a role in increasing the hole injection efficiency. That is, an undoped In _x2 Ga _{1 -x2} N layer (0 ≦ x ₂ <1) is formed thicker than the other barrier layers as the final layer of the MQW active layer, and a p-type impurity such as Mg is formed thereon at a high concentration. By growing a thin film made of doped p-type Al _x Ga _1-x N (0.1 <x <0.5) at a low temperature, the active layer containing In is protected from decomposition, and p-type Al _x Ga _1-x from the N layer such as Mg undoped _{in x2} Ga _1-x2 N layer p-type impurity can be improved hole injection efficiency to diffuse active layer.

  Among the p-type nitride semiconductor layers, a ridge stripe is formed up to the middle of the p-type light guide layer, and further, a protective film, a p-type electrode, an n-type electrode, a p-pad electrode, and an n-pad electrode are formed to form a semiconductor laser. Is configured.

  The laser light used for the first light-emitting element 101 preferably has an emission peak wavelength from 350 nm to 500 nm. By using a laser beam in this range, it is possible to use the fluorescent material 400 with good wavelength conversion efficiency. Moreover, deterioration of the resin mixed with the fluorescent material 400 can be suppressed by setting the amount in this range. As the laser light used for the second light-emitting element 102, one having an emission peak wavelength from 573 nm to 780 nm can be used.

<Light guide plate>
The light guide plate 200 guides the light from the first light emitting element 101 and the second light emitting element 102 which are the point light sources 100 to the outside and serves as a distributed light source.

  The light extraction surface 200a of the light guide plate 200 can take various shapes such as a substantially rectangular shape, a substantially square shape, a substantially polygonal shape, a substantially circular shape, and a substantially elliptical shape. The light guide plate 200 can be a substantially rectangular parallelepiped, and is preferably provided so that the incident side surface 200b of the light source 100 is wide and the opposite side surface 200b is narrow. This is because the incident light is efficiently extracted to the light extraction surface 200a side.

  The side surface 200c of the light guide plate 200 allows not only the light source to be incident from only one side surface, but also the light source to be incident from two opposite surfaces, two adjacent surfaces, three adjacent surfaces, or the like. This is because light is extracted from the light extraction surface 200a with high output and uniformity.

  As the material of the light guide plate 200, acrylic resin, polycarbonate resin, amorphous polyolefin resin, polystyrene resin, norbornene resin, cycloolefin polymer (COP), glass, or the like can be used. Although the materials of these light guide plates 200 have different refractive indexes, the light diffusion can be controlled by selecting the angle and number of notched prisms formed on the incident end face of the light guide plate. Is not subject to any restrictions. The light guide plate 200 is formed by injection molding the above material into a mold. The mold is not limited to a flat one, but can be provided with a slit (notch) or an inclination, and can have any shape depending on the application. As processing methods, there are a blast processing method, an etching processing method, and the like, but electric discharge processing is most preferable. In order to form a pattern shape on the mold by electric discharge machining, the following conditions are adjusted as appropriate. The electric discharge machining conditions are such that the pulse width is 1 μsec to 200 μsec, and the current value is changed in the range of 0.1 A to 20 A. As other electric discharge machining conditions, the distance between the electrode and the mold is set in the range of 0.5 μm to 1000 μm, preferably 1 μm to 100 μm. By performing operations such as gradually moving the distance between the electrode and the mold within the above range and gradually separating the distance from each other, it is possible to make the pear-ground surface of the emitting surface and the reflecting surface into a gradation shape. Thereby, the light-guide plate which formed the pear ground continuously can be provided.

  The light guide plate 200 includes a fluorescent material 400 that absorbs at least part of the light from the first light emitting element 101 and emits light of different wavelengths. Here, “having a fluorescent material” means that the fluorescent material is contained in the light guide plate, a coating containing the fluorescent material is attached to the light guide plate, and the fluorescent material is introduced through an adhesive or the like. It means that it is attached to the surface. In the first embodiment, a film containing the fluorescent material 400 is attached to the light guide plate 200. As a result, the light guide plate 200 can be easily manufactured, and a resin that is resistant to light degradation can be manufactured. Moreover, the light-guide plate which heats and shape | molds can also be used. On the other hand, the light guide plate 200 can also apply the fluorescent material 400 to the surface of the light extraction surface. Further, the fluorescent material 400 can be mixed and molded in the light guide plate 200. At this time, in addition to the fluorescent material 400 being uniformly disposed inside the light guide plate 200, the fluorescent material 400 may be disposed on the light extraction surface 200a or the bottom surface 200b by allowing the fluorescent material 400 to settle.

  It is preferable to provide a reflecting member on the bottom surface 200b and the side surface 200c of the light guide plate 200. This is because the light incident from the light source 100 is efficiently guided to the light extraction surface 200a. Further, it is preferable to provide an ultraviolet absorbing member or an ultraviolet reflecting member on the light extraction surface 200 a of the light guide plate 200. This is because ultraviolet rays affect the vision and the human body, and it is preferable to reduce the amount of light emitted from the light guide plate 200 to the outside as much as possible. As the reflecting member, Ag, Cu, Au, Pt, Al, or the like that efficiently reflects visible light is preferable.

<Light diffusion member>
In the light emitting device, it is preferable to provide a light diffusion member 300 between the light source 100 and the light guide plate 200. The term “between the light source 100 and the light guide plate 200” means between the paths where the light emitted from the light source 100 enters the light guide plate 200, and the light emitted from the light source 100 directly enters the light guide plate 200. It includes not only during the interval, but also when the light emitted from the light source 100 enters the light guide plate 200 via the indirect member. The light diffusing member 300 is preferably configured as a separate component from the light guide plate 200, but may be configured as an integral component. The light diffusing member 300 is a member for diffusing the light emitted from the light source 100. For example, when a laser diode is used for the light source 100, since the straightness of laser light is strong, it is difficult for light to be diffused when entering the light guide plate 200, and it is difficult to extract light uniformly from the light extraction surface 200a. Further, the light diffusing member 300 may change the shape of the laser light.

  As the light diffusing member 300, a generally used cylindrical lens or rod lens can be used. As the material of the light diffusion member 300, acrylic resin, polycarbonate resin, amorphous polyolefin resin, polystyrene resin, norbornene resin, cycloolefin polymer (COP), glass, or the like is used. The light diffusing member 300 may be mixed with fine particles of an inorganic substance such as inorganic glass.

<Fluorescent substance>
As the fluorescent material 400, a fluorescent material having a light emission peak wavelength on the longer wavelength side than the light emission peak wavelength of the first light emitting element 101 can be used. As a result, light can be emitted efficiently.

  In addition, a fluorescent material 400 having a light emission peak wavelength between the light emission peak wavelength of the first light emitting element 101 and the light emission peak wavelength of the second light emitting element 102 can also be used. Accordingly, since the light of the fluorescent material 400 can be mainly adjusted by the light from the first light emitting element 101, the color mixture of the light from the fluorescent material 400 and the light of the second light emitting element 102 can be easily adjusted. Can do. In addition, the absorption of light of the fluorescent material 400 is on the shorter wavelength side than the emission peak wavelength of the second light emitting element, and is reflected with almost no wavelength conversion. Therefore, it is considered that the fluorescent material 400 has a light diffusing action. .

  The fluorescent material 400 may be mixed into the light guide plate 200 to form the light guide plate 200. The fluorescent material 400 can be configured to be uniformly dispersed in the light guide plate 200, and is also placed on the light extraction surface 200a or bottom surface 200b side by being settled or floated in the light guide plate 200 by the specific gravity of the particles of the fluorescent material 400. It is also possible to adopt a configuration to make it. In addition, the fluorescent material 400 may be mixed in a film such as a silicone resin or an epoxy resin to form a sheet on a flat plate, and this sheet-shaped film may be attached to the light guide plate 200. Further, the fluorescent material 400 may be mixed in a film made of silicone resin, epoxy resin, or the like, and applied and adhered to the surface of the light guide plate 200 using a printing unit, an inkjet spraying unit, or the like. The fluorescent material 400 need not be only one type, and two or more types may be mixed and used.

  As the fluorescent material 400, for example, the following can be used. As the fluorescent material 400, a phosphor that emits blue light, a phosphor that emits green light, a phosphor that emits yellow light, a phosphor that emits red light, or the like can be used. For example, a nitride-based phosphor / oxynitride-based phosphor mainly activated by a lanthanoid element such as Eu or Ce, an alkali mainly activated by a lanthanoid element such as Eu or a transition metal element such as Mn Earth halogen apatite phosphor, alkaline earth metal borate halogen phosphor, alkaline earth metal aluminate phosphor, alkaline earth silicate, alkaline earth sulfide, alkaline earth thiogallate, alkaline earth silicon nitride From organic and organic complexes mainly activated by rare earth aluminates, rare earth silicates, or lanthanoid elements such as Eu, mainly activated by lanthanoid elements such as germanate or Ce It is preferable that it is at least any one selected. As specific examples, the following phosphors can be used, but are not limited thereto.

A nitride phosphor mainly activated by a lanthanoid element such as Eu or Ce is M ₂ Si ₅ N ₈ : Eu (M is at least one selected from Sr, Ca, Ba, Mg, Zn). There is.) In addition to M ₂ Si ₅ N ₈ : Eu, MSi ₇ N ₁₀ : Eu, M _1.8 Si ₅ O _0.2 N ₈ : Eu, M _0.9 Si ₇ O _0.1 N ₁₀ : Eu (M Is at least one selected from Sr, Ca, Ba, Mg, and Zn.

An oxynitride phosphor mainly activated by a lanthanoid element such as Eu or Ce is MSi ₂ O ₂ N ₂ : Eu (M is at least one selected from Sr, Ca, Ba, Mg, Zn) Etc.).

Alkaline earth halogen apatite phosphors mainly activated by lanthanoid-based elements such as Eu or transition metal-based elements such as Mn include M ₅ (PO ₄ ) ₃ X: R (M is Sr, Ca, Ba). X is at least one selected from F, Cl, Br and I. R is any one of Eu, Mn, Eu and Mn. Etc.).

The alkaline earth metal borate phosphor has M ₂ B ₅ O ₉ X: R (M is at least one selected from Sr, Ca, Ba, Mg, Zn. X is F, Cl , Br, or I. R is Eu, Mn, or any one of Eu and Mn.).

Examples of the alkaline earth sulfide phosphor include La ₂ O ₂ S: Eu, Y ₂ O ₂ S: Eu, and Gd ₂ O ₂ S: Eu.

Examples of rare earth aluminate phosphors mainly activated with lanthanoid elements such as Ce include Y ₃ Al ₅ O ₁₂ : 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, and the like (Y, Gd) 3 (Al , Ga) YAG -based phosphor represented by the composition formula of _{5 O 12.}

The alkaline earth metal silicate is preferably an alkaline earth metal orthosilicate represented by the following general formula.
(2-x-y) SrO · x (Ba, Ca) O · (1-a-b-c-d) SiO 2 · aP 2 O 5 bAl 2 O 3 cB 2 O 3 dGeO 2: yEu 2+ ( Equation Medium, 0 <x <1.6, 0.005 <y <0.5, 0 <a, b, c, d <0.5.)
(2-x-y) BaO · x (Sr, Ca) O · (1-a-b-c-d) SiO 2 · aP 2 O 5 bAl 2 O 3 cB 2 O 3 dGeO 2: yEu 2+ ( Equation (Inside, 0.01 <x <1.6, 0.005 <y <0.5, 0 <a, b, c, d <0.5.)
Here, preferably, at least one of the values of a, b, c and d is greater than 0.01.

As a phosphor composed of an alkaline earth metal salt, in addition to the alkaline earth metal silicate described above, an alkaline earth metal aluminate or Y (V, P, Si) O ₄ activated with europium and / or manganese is used. : Eu, or an alkaline earth metal-magnesium-disilicate represented by the following formula:

Me (3-xy) MgSi ₂ O ₃ : xEu, yMn (wherein 0.005 <x <0.5, 0.005 <y <0.5, Me represents Ba and / or Sr and / or Or Ca.)
Alkaline earth metal aluminate phosphors include SrAl ₂ O ₄ : R, Sr ₄ Al ₁₄ O ₂₅ : R, CaAl ₂ O ₄ : R, BaMg ₂ Al ₁₆ O ₂₇ : R, BaMg ₂ Al ₁₆ O ₁₂ : R, BaMgAl ₁₀ O ₁₇ : R (R is Eu, Mn, or any one of Eu and Mn).

Other phosphors include ZnS: Eu, Zn ₂ GeO ₄ : Mn, MGa ₂ S ₄ : Eu (M is at least one selected from Sr, Ca, Ba, Mg, Zn. X is At least one selected from F, Cl, Br, and I). M ₂ Si ₅ N ₈ : Eu, MSi ₇ N ₁₀ : Eu, M _1.8 Si ₅ O _0.2 N ₈ : Eu, M _0.9 Si ₇ O _0.1 N ₁₀ : Eu (M is , Sr, Ca, Ba, Mg, and Zn.).

  The phosphor described above contains at least one selected from Tb, Cu, Ag, Au, Cr, Nd, Dy, Co, Ni, and Ti instead of Eu or in addition to Eu as desired. You can also.

  Moreover, it is fluorescent substance other than the said fluorescent substance, Comprising: The fluorescent substance which has the same performance and effect can also be used.

  These phosphors emit light in yellow, red, green, blue, or an intermediate color such as yellow, blue-green, or orange by excitation light from the light source 100. By appropriately combining these phosphors, light emitting devices having various emission colors can be manufactured.

  A fluorescent pigment, a fluorescent dye, or the like can also be used as the fluorescent substance.

  In addition, quantum dots (nanoparticles) can be used as the fluorescent material. Quantum dots (nanoparticles) are nanosized particles having different emission colors depending on the particle size. For example, particle dots such as nano-sized cadmium selenide particles (CdSe) can be used. This emits light on the longer wavelength side as the particle size increases. For example, when the average particle size is 2.4 nm, the color is blue at 2.8 nm, green at 3.4 nm, orange at 3.8 nm, red at 4.2 nm, and red at 4.2 nm.

<Diffusion material>
Further, the light guide plate 200 may contain a diffusing agent. As a specific diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide or the like is preferably used. As a result, light incident from the light source 100 is dispersed, and uniform light is emitted from the light extraction surface 200a.

<Second Embodiment>
FIG. 3 is a schematic plan view showing a light emitting device according to the present invention. FIG. 4 is a schematic cross-sectional view showing a light emitting device according to the present invention. FIG. 4 is a schematic cross-sectional view taken along the line II-II in FIG. A description of portions that are substantially the same as those in the first embodiment will be omitted.

  The light emitting device according to the second embodiment includes a light source 110, a light guide plate 210 that transmits light from the light source 110, and a light diffusion member 310 provided between the light source 110 and the light guide plate 210. The light diffusing member 310 is attached to the side surface of the light guide plate 210. As a result, the integration efficiency can be improved. The light guide plate 210 has a flat plate shape, light diffusion members 310 are mounted on two adjacent side surfaces 210c, and reflection members are provided on the remaining two side surfaces 210c and the bottom surface 210b. The two light sources 110 are arranged so as to be substantially parallel to the adjacent side surface 210c of the light guide plate 210. The light source 110 has a first light emitting element and a second light emitting element. The first light emitting element is a laser diode having an emission peak wavelength near 400 nm, and the second light emitting element has an emission peak wavelength in the red region. Is a laser diode. The fluorescent material 410 is a material having an emission peak wavelength in blue-green due to light from the first light emitting element, for example, an oxynitride phosphor. Accordingly, it is possible to provide a light emitting device that emits white light by blue-green light from the fluorescent material and red light from the second light emitting element. In the light guide plate 210, a film containing the fluorescent material 410 is attached to the light extraction surface 210a. The coating is applied not only to the light extraction surface 200 a but also to the light diffusing member 310, thereby reducing light leakage from the light diffusing member 310. This coating is configured so that the fluorescent material 410 is very densely packed and hardly emits light from the light source 110 to the outside. The light guide plate 210 uses a translucent glass member. The light extraction surface 210a of the light guide plate 210 is configured to emit light reflected and scattered inside the light guide plate 210 to the outside. The light diffusing member 310 diffuses light from the light source 110. Unlike the first embodiment, since the light diffusing member 310 is mounted on the light guide plate 210, it is not necessary to adopt a condensing lens shape, and the reflection between the light diffusing member 300 and the light guide plate 210 is not necessary. Therefore, it is possible to guide the light guide plate 200 efficiently. The light guide plate 210 contains a diffusing material 510, and light is dispersed almost uniformly.

<Third Embodiment>
The following embodiments can be replaced with a part of the light emitting device described above and below. The third embodiment and the fourth embodiment relate to a light source.

  As the third embodiment, for example, there are various modifications of the light source 120. FIG. 5 is a schematic plan view showing a light extraction surface of the light source.

  The light source 120 is a horizontally long elliptical outlet that extends along the side of the light guide plate. This is because the point light source is efficiently incident on the side surface of the flat light guide plate. The number of the light sources 120 is also appropriately changed according to the size of the light guide plate. Further, the light source 120 may have a configuration in which two first light emitting elements are arranged and a second light emitting element is arranged therebetween.

<Fourth embodiment>
As the fourth embodiment, one in which a plurality of first light-emitting elements 131 and second light-emitting elements 132 are arranged as one set can also be used. FIG. 6 is a schematic plan view showing a light extraction surface of the light source.

  Unlike the third embodiment, in the fourth embodiment, two circular emission ports are arranged along the side surface direction of the light guide plate. The two light emission ports are a set of the first light emitting element 131 and the second light emitting element 132. As a result, the light emitted from the pair of light emitting elements is uniformly mixed.

<Fifth embodiment>
The fifth to ninth embodiments relate to a light guide plate.

  The fifth embodiment relates to a light guide plate 220 having an inclined bottom surface. FIG. 7 is a schematic cross-sectional view showing the light guide plate.

  In order to guide the light incident from the side surface of the light guide plate 220 to the light extraction surface 200a, the bottom surface of the light guide plate 220 is inclined. The inclination angle α is preferably greater than 0 ° and about 15 °, but most preferably about 1 ° to 3 °. Since the light has a straight traveling property, the direction of the light from the light source incident in parallel to the light extraction surface 200a does not change unless it irradiates any member. Therefore, the parallel light is irradiated and reflected on the bottom surface of the light guide plate 220 and guided to the light extraction surface 200a side. The light guide plate 220 is formed by mixing the fluorescent material 420 substantially uniformly.

<Sixth Embodiment>
In the sixth embodiment, a fluorescent material 430 is fixed to a light guide plate 230. FIG. 8 is a schematic cross-sectional view showing the light guide plate.

  The fluorescent material 430 is fixed to the light extraction surface side of the light guide plate 230 by using an ink jet spraying means, a plating means, a printing means or the like. In the case where the fluorescent material 430 does not have adhesiveness, the fluorescent material 430 is fixed using an adhesive such as an epoxy resin coated on the surface of the fluorescent material 430. The light extraction surface is densely filled with the fluorescent material 430 to efficiently convert the wavelength of the light from the light source.

<Seventh embodiment>
In the seventh embodiment, a fluorescent material 440 is arranged on the light extraction surface side inside the light guide plate 240. FIG. 9 is a schematic cross-sectional view showing the light guide plate.

  A fluorescent material 440 and a diffusion material 520 are mixed in the light guide plate 240. The fluorescent material 440 is disposed substantially uniformly on the light extraction surface side of the light guide plate 240. The diffusing agent 520 is uniformly diffused inside the light guide plate 240. Reflective members are provided on the side and bottom surfaces of the light guide plate 240. The bottom surface of the light guide plate 240 is inclined. As a result, the light incident from the side surface of the light guide plate 240 is applied to the diffusing agent 520 to diffuse the light. The diffused light is applied to the bottom and side surfaces, reflected, and applied to the fluorescent material 440 disposed on the light extraction surface side. Light that has been absorbed and wavelength-converted by the fluorescent material 440 is emitted to the outside from the light extraction surface. On the other hand, the fluorescent material 440 may be directly irradiated without being irradiated on the bottom and side surfaces.

  Concavities and convexities are formed on the light extraction surface of the light guide plate 240. As a result, the light extraction efficiency can be improved, or the coherency of the laser diode can be canceled.

  The light guide plate 240 is a mixture of a diffusing agent 520 that is approximately equal to the specific gravity of the material of the light guide plate 240 and a fluorescent material 440 that is heavier than the specific gravity of the material of the light guide plate 240. Then, the light extraction surface side is faced down and left for a predetermined time. As a result, the fluorescent material 440 having a high specific gravity settles and hardens. Thereafter, the reflecting member is fixed to predetermined side surfaces and the bottom surface of the light guide plate 240.

  Thereby, the ultraviolet light of the first light emitting element can be prevented from leaking from the light guide plate 240.

<Eighth Embodiment>
The eighth embodiment is almost the same as the seventh embodiment except that the arrangement of the fluorescent material 450 is different. FIG. 10 is a schematic cross-sectional view showing the light guide plate.

  A fluorescent material 450 and a diffusing agent 530 are disposed inside the light guide plate 250. The fluorescent material 450 is disposed on the bottom surface of the light guide plate 250. In some cases, it is also arranged on the side. Also in this case, the fluorescent material 450 and the material of the light guide plate 250 are arranged using the specific gravity difference. Thereby, the light incident from the light source is irradiated to the fluorescent material 450 arranged on the bottom surface and the side surface and is emitted to the light extraction surface side. The light whose wavelength has been converted by the fluorescent material 450 is diffused by the diffusing agent 540. As a result, light from the second light emitting element is emitted from the light extraction surface, and the light of the fluorescent material 540 is more uniformly mixed.

<Ninth embodiment>
In the ninth embodiment, the diffusing agent 540 and the fluorescent material 460 are uniformly diffused inside the light guide plate 260. FIG. 11 is a schematic cross-sectional view showing the light guide plate.

  The diffusing agent 540 and the fluorescent material 460 are uniformly diffused inside the light guide plate 260. Accordingly, the light from the second light emitting element is reflected by the fluorescent material 460 without being absorbed, and thus the fluorescent material 460 acts as a diffusing agent. Thereby, it is possible to uniformly mix colors.

<Tenth Embodiment>
In the tenth embodiment, the film 600 is fixed to the surface of the light guide plate 270. FIG. 12 is a schematic cross-sectional view showing a light emitting device according to the present invention.

  A fluorescent material 470 is disposed on the light extraction surface of the light guide plate 270. The film 600 is adsorbed on the light extraction surface of the light guide plate 270. This film 600 does not transmit ultraviolet light but transmits only visible light. The light from the light source 120 passes through the light diffusion member 320 and enters the side surface of the light guide plate 270. A non-reflective coating is applied to the incident surface side of the light diffusing member 320 and the side surface of the light guide plate 270 on the incident surface side. Thereby, the incident loss can be reduced. The light diffusing member 320 has a condensing lens shape, condenses the light from the light source 120 and makes it incident on the side surface of the light guide plate 270.

<Eleventh embodiment>
In the eleventh embodiment, an inclination is provided so that the central portion of the light guide plate 280 is raised. FIG. 13 is a schematic cross-sectional view showing the light guide plate.

  The bottom surface 280b of the light guide plate 280 is provided with an inclination. This inclination has a central portion recessed toward the inner side of the light guide plate 2. This prevents light incident from one side from escaping to the opposite side. Further, unevenness can be provided on the bottom surface of the light guide plate 280 to enhance the light scattering effect.

<Twelfth embodiment>
In the twelfth embodiment, the light guide plate 290 and the light diffusing member are integrally molded. FIG. 14 is a schematic cross-sectional view showing a light emitting device according to the present invention.

  The light guide plate 290 has a rounded side surface so that light from the light source 140 can be easily incident and diffused. The light extraction surface of the light guide plate 290 is coated with a film mixed with the fluorescent material 490.

<Example 1>
The first embodiment includes a light source 100, a light guide plate 200, and a light diffusing member 300. FIG. 1 is a schematic perspective view showing a light emitting device according to the present invention. FIG. 2 is a schematic cross-sectional view showing a light emitting device according to the present invention. Reference is also made to the first embodiment described above.

  A GaN laser diode is used for the first light emitting element 101 of the light source 100. The laser diodes of the first light emitting element 101 and the second light emitting element 102 are arranged in the vertical direction with respect to the light guide plate 200. As the first light emitting element 101, one having a light emission peak wavelength in a blue region is used. As the second light emitting element 102, one having an emission peak wavelength in the red region is used.

  The light guide plate 200 uses a glass material that is a base transparent to the laser light source. The light guide plate 200 is a flat plate having a thickness of about 1 mm. A fluorescent material 400 is applied to the light extraction surface 200 a of the light guide plate 200. The fluorescent material 400 uses a YAG phosphor. The bottom surface 200b and the side surface 200c (excluding the light source side) of the light guide plate 200 are coated with Ag. A non-reflective coating is applied to the side surface 200c (light source side) of the light guide plate 200.

  A cylindrical lens is used for the light diffusion member 300. The cylindrical lens is made of an acrylic material and has a focal length of 3 mm. The light incident surface and the light output surface of the cylindrical lens are provided with a non-reflective coating, and the incident loss is 5% or less. As a result, the beam width at the entrance surface of the light guide plate 200 is about 0.5 mm on the short side, and 80% or more of the total light output can be injected into the glass.

  In general, light incident on a transparent mother body is repeatedly reflected and scattered inside the light guide plate 200 and finally irradiated to the fluorescent material 400. Further, the light incident on the back surface is scattered as a standing wave, and is irradiated on the fluorescent material 400 to be converted into white light. By using this optical arrangement, laser light with high coherence from the laser diode is not directly incident on the human eye.

  Accordingly, the YAG phosphor is excited by the blue light from the first light emitting element 101 and emits yellow light, and white light that is mixed color light is emitted from the light guide plate 200. Further, in order to change the color tone, the second light emitting element 102 can be made incident on the light guide plate 200 so as to have a slightly reddish white. Light from the first light-emitting element 101 and the second light-emitting element 102 is repeatedly diffused, reflected, and scattered by the cylindrical lens and the light guide plate 200, and uniform light is emitted from the light extraction surface 200 a of the light guide plate 200. .

<Example 2>
The second embodiment includes a light source 110, a light guide plate 210, and a light diffusing member 310. FIG. 3 is a schematic perspective view showing a light emitting device according to the present invention. FIG. 4 is a schematic cross-sectional view showing a light emitting device according to the present invention. 5 is a schematic plan view showing the light extraction surface of the light source. Reference is also made to the second embodiment described above.

  As in the first embodiment, sufficient luminance can be obtained only by irradiating the laser beam from only one side of the light guide plate 200. However, in order to obtain higher luminance, the laser beam is emitted from not only one side but also two or more sides. It is also possible to irradiate. By irradiating a plurality of laser beams, it is possible to obtain several times the luminance.

  Two sets of light sources 110 are used to make light incident from two side surfaces of the light guide plate 210. Two first light emitting elements are used for one set of light sources, and one second light emitting element is used between them. The first light-emitting element uses a GaN-based laser diode having an emission peak wavelength near 405 nm. A second light emitting element having an emission peak wavelength in the red region is used.

The light guide plate 210 is made of translucent glass and is coated with Ag except for the portion where the light from the light source 110 is incident and the light extraction surface 210a. A light-diffusing member 300 is attached to the light guide plate 210 as a cylindrical lens. The light extraction surface 210 a of the light guide plate 210 is coated with a film mixed with the fluorescent material 410. The fluorescent material 410 includes an alkaline earth halogen apatite phosphor represented by Ca ₁₀ (PO ₄ ) ₆ (Cl, Br) ₂ : Eu, and an oxynitride phosphor represented by BaSi ₂ O ₂ N ₂ : Eu. Is used.

  The first light emitting element excites an alkaline earth halogen apatite phosphor and an oxynitride phosphor, and emits white light by mixing the light from the phosphor and the light from the second light emitting element. Can be provided.

  The light emitting device of the present invention can be used for lighting fixtures, displays, liquid crystal backlights, and the like.

It is a schematic perspective view which shows the light-emitting device which concerns on this invention. It is a schematic sectional drawing which shows the light-emitting device based on this invention. 1 is a schematic plan view showing a light emitting device according to the present invention. It is a schematic sectional drawing which shows the light-emitting device based on this invention. It is a schematic plan view which shows the light extraction surface of a light source. It is a schematic plan view which shows the light extraction surface of a light source. It is a schematic sectional drawing which shows a light-guide plate. It is a schematic sectional drawing which shows a light-guide plate. It is a schematic sectional drawing which shows a light-guide plate. It is a schematic sectional drawing which shows a light-guide plate. It is a schematic sectional drawing which shows a light-guide plate. It is a schematic sectional drawing which shows the light-emitting device based on this invention. It is a schematic sectional drawing which shows a light-guide plate. It is a schematic sectional drawing which shows the light-emitting device based on this invention. It is a schematic perspective view which shows the conventional distributed light source device.

Explanation of symbols

100, 110, 120, 130, 140 Light source 101 First light emitting element 102 Second light emitting element 200, 210, 220, 230, 240, 250, 260, 270, 280, 290 Light guide plate 200a, 210a, 280a Light extraction Surface 200b, 210b, 280b Bottom surface 200c, 210c, 280c Side surface 300, 310, 320 Light diffusing member 400, 410, 420, 430, 440, 450, 460, 470, 480, 290 Fluorescent substance 510, 520, 530, 540 Diffusion Material 600 film

Claims (18)

A light-emitting device having a light source and a light guide plate that transmits light from the light source,
The light source includes a first light emitting element, and a second light emitting element having a light emission peak wavelength on a longer wavelength side than the light emission peak wavelength of the first light emitting element,
The light guide plate includes a fluorescent material that emits light of different wavelengths by absorbing at least part of the light from the first light emitting element,
At least light from the second light emitting element and light from the fluorescent material are mixed and emitted to the outside. The light emitting device according to claim 1, wherein the light emitting device further emits light from the first light emitting element after mixing. 2. The light-emitting device according to claim 1, wherein one of the first light-emitting element and the second light-emitting element is a laser diode. The light emitting device according to claim 1, wherein the fluorescent material has an emission peak wavelength on a longer wavelength side than an emission peak wavelength of the first light emitting element. 2. The light emitting device according to claim 1, wherein the fluorescent material has a light emission peak wavelength between a light emission peak wavelength of the first light emitting element and a light emission peak wavelength of the second light emitting element. . The light emitting device according to claim 1, wherein the fluorescent material is a quantum dot. The light emitting device according to claim 1, wherein the first light emitting element is visible light. The light emitting device according to claim 1, wherein the first light emitting element has an emission peak wavelength between 380 nm and 495 nm. The light emitting device according to claim 1, wherein the first light emitting element is ultraviolet light. 2. The light emitting device according to claim 1, wherein the light source includes a plurality of the first light emitting elements and the second light emitting elements. A light emitting device comprising: a light source; a light guide plate that transmits light from the light source; and a light diffusion member provided between the light source and the light guide plate,
The light source comprises a laser diode;
The light guide plate has a fluorescent material that absorbs at least part of light from the laser diode and emits light of different wavelengths,
At least one of the light from the laser diode and the light from the fluorescent material is emitted to the outside. The light-emitting device according to claim 1, wherein the light guide plate contains a diffusing material. The light emitting device according to claim 1 or 11, wherein the fluorescent material is applied to a surface of the light guide plate from which light is extracted. The light-emitting device according to claim 1, wherein the light guide plate has the fluorescent material disposed on a surface side from which light is extracted. The light-emitting device according to claim 1, wherein the fluorescent material is disposed on at least a part of a vicinity of a surface different from a surface from which the light is extracted. The light-emitting device according to claim 1, wherein the light guide plate has an ultraviolet absorber disposed inside or near the outside of a light extraction surface. The light emitting device according to claim 12, wherein the diffusing material is dispersed substantially uniformly on the light guide plate. The light emitting device according to claim 1, wherein a light diffusing member is provided between the light source and the light guide plate.

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