JP2000031531A - Light emitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitter which has stable light emission property by putting the mixture ratio of light surely and easily in desired balance. SOLUTION: This light emitter is equipped with a light emitting element 11 which emits the primary light of first wavelength, and a first phosphor 17 which absorbs the primary light and emits the secondary light of second wavelength, a second phosphor 18 which absorbs the secondary light of the second wavelength and emits the secondary light of the third wavelength. Then, the second phosphor 18 stabilizes the balance of an obtained light spectrum by being constituted as one which is low in absorptivity to the first wavelength and substantially does not converts the wavelength, and even if the wavelength of the primary light emitted from the light emitting element or the intensity change, the obtained light spectrum does not change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly to a light emitting device in which a light emitting device such as a semiconductor light emitting device and a wavelength conversion means such as a phosphor are combined.

[0002]

2. Description of the Related Art Light-emitting devices in which a semiconductor light-emitting element such as an LED (light emitting diode) and a phosphor are combined are attracting attention as inexpensive and long-life light-emitting devices, and are being widely used. In particular, white light emitting devices
Various applications are expected as a light emitting device instead of a fluorescent lamp or as a light source for a display device.

FIG. 6 is a schematic sectional view showing a conceptual configuration of a conventional white light emitting type light emitting device. That is, in the conventional light emitting device, the blue light emitting L
The ED 111 is mounted, and its periphery is molded with a resin 112. The LEDs 111 are appropriately wired by wires 114. In addition, resin 112
The phosphor 117 is applied on the substrate. Further, the periphery thereof is sealed with a sealing resin 113.

[0006] In the light emitting device of FIG.
A part of the primary light blue light emitted from D111 is absorbed by the phosphor 117, and yellow light is emitted as secondary light.
That is, white light is generated by the blue light emitted from the LED 111 and the yellow light emitted from the phosphor 117.

[0005]

However, as a result of trial manufacture and evaluation by the present inventors, it has been found that the conventional light emitting device as shown in FIG. 6 has the following problems. That is, (1) the white balance varies greatly from device to device. (2) White balance changes greatly due to changes in the supplied current value. (3) White balance changes significantly due to fluctuations in ambient temperature. (4) The change in white balance due to the aging of the LED 111 is large.

[0006] All of these problems result from the essential characteristics of the blue light emitting LED 111 used as a semiconductor light emitting device. That is, the blue light emitting LED 1
It is difficult to control the composition of indium gallium nitride (InGaN) used as the eleventh light emitting layer strictly, and the emission wavelength tends to fluctuate for each growth wafer.
Further, it has a characteristic that the emission wavelength fluctuates relatively largely depending on the current and temperature supplied to the LED. Further, when the current is supplied and the light emitting operation is continued, the light emission wavelength tends to fluctuate.

As described above, when the wavelength of the blue light emitted from the blue light emitting LED 111 fluctuates, the balance of the intensity with the yellow light emitted from the phosphor 17 is lost, and the chromaticity coordinates are greatly shifted. As a result, it has been found that a problem occurs in that the white balance of the output white light greatly changes.

As a method for solving this problem, R (red)
There is also a method of using a phosphor that emits light of three colors of G (green) and B (blue). However, in this case, it is necessary to precisely adjust the mixing ratio of the three types of phosphors, and it is not easy to mix them in a predetermined balance. Further, when the phosphors are mixed and applied, there is a disadvantage that it is difficult to realize a desired uniform mixing form due to the influence of separation caused by the difference in specific gravity of each phosphor particle.

The present invention has been made based on the recognition of such a unique problem. That is, an object of the present invention is to provide a light-emitting device having a stable light-emitting characteristic by reliably and easily adjusting a mixing ratio of light to a desired balance.

[0010]

In order to achieve the above object, a light emitting device according to the present invention comprises a light emitting element for emitting light of a first wavelength and a light emitting element for absorbing the light of the first wavelength. A first wavelength converting means for emitting light of a wavelength of the second wavelength, and a second wavelength converting means for absorbing light of the second wavelength and emitting a light of a third wavelength. Even if the first wavelength emitted from the light emitting element changes, the balance between the light of the second wavelength and the light of the third wavelength can be stabilized.

Here, the second wavelength is longer than the first wavelength, the third wavelength is longer than the second wavelength, and the second wavelength converting means includes By not substantially absorbing the light of the wavelength of
The balance between the light of the second wavelength and the light of the third wavelength can be extremely stabilized.

In a preferred embodiment of the present invention, the first wavelength converting means is a fluorescent material, and the second wavelength converting means is a fluorescent material.

Further, the light of the first wavelength is ultraviolet light, the light of the second wavelength is blue light, and the light of the third wavelength is
Is characterized by being yellow light, white light with extremely stable white balance can be obtained.

Further, the light-emitting element is a semiconductor light-emitting element made of a nitride semiconductor, so that a high-luminance light-emitting device can be realized.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view illustrating a conceptual configuration of a light emitting device according to an embodiment of the present invention.
That is, the light emitting device shown in FIG. 1 is generally called a “vertical LED”, in which a light emitting element 11 is mounted on a cup portion of a lead frame 16, and the periphery thereof is molded with a resin 12. It is desirable that the resin 12 is made of a material that absorbs less light emitted from the light emitting element 11. The light emitting elements 11 are appropriately wired by wires 14. In addition, a first wavelength conversion unit 18 and a second wavelength conversion unit 17 are provided on the resin 12.
Further, the periphery thereof is sealed with a sealing resin 13.

Here, the first wavelength converting means 18 absorbs the light of the first wavelength emitted from the light emitting element 11 and converts it into light of the second wavelength longer than that. For example, when an LED that emits ultraviolet light is used as the light emitting element 11, a phosphor that emits blue secondary light when excited by the ultraviolet light can be used.

On the other hand, the second wavelength conversion means 17 has a second wavelength having the second wavelength emitted from the first wavelength conversion means 18.
The secondary light is absorbed and converted into secondary light having a longer third wavelength. As the second wavelength conversion means 17, for example, a phosphor that is excited by blue light emitted from the phosphor 18 and emits yellow secondary light can be used. here,
The phosphor 17 has a low absorptance for light of the first wavelength emitted from the light emitting element 11. That is,
It is desirable that the phosphor 17 has a peak of absorptance in the wavelength region of the secondary light emitted from the phosphor 18.

According to the above-described specific example, in the light emitting device of the present invention, the ultraviolet light of the primary light emitted from the ultraviolet light emitting LED 11 is absorbed by the phosphor 17 and the blue light is emitted as the secondary light. Released. Then, part of the blue light is absorbed by the phosphor 17 and yellow light is emitted as secondary light. The phosphor 17 has a low absorptivity to ultraviolet light emitted from the LED 11, and does not substantially cause wavelength conversion. Then, white light is generated by the blue light emitted from the phosphor 18 and the yellow light emitted from the phosphor 17.

As an example of the phosphor that can be used in the present invention, as the blue light-emitting phosphor 18 excited by ultraviolet light, there is, for example, a model 801EJ manufactured by Toshiba. The specific gravity of 801EJ is 4.2. On the other hand, as the yellow light-emitting phosphor 17 excited by blue light, YAG
(Ce), that is, (Y _1-a Gd _a ) ₃ (Al _1-b G _ab ) ₅ O
₁₂ : Ce is present. The specific gravity of YAG (Ce) is also about 4.
2.

As an example of the method of forming the layers of the phosphors 17 and 18, the following method can be mentioned. (1) Cast 801EJ. That is, the phosphor is dispersed in a solvent, applied to the surface of the resin 12, heated, cured and cured. Thus, the layer of the blue phosphor 18 can be formed. Next, similarly, YAG (Ce) is cast thereon. This series of methods can be used irrespective of the magnitude of the specific gravity of the phosphor. (2) A solvent in which 801EJ is dissolved and a solvent in which YAG (Ce) is dissolved are dropped on the surface of the resin 12. At this time, in consideration of the specific gravity of the phosphor particles, the viscosity and the curing speed of the solvent, etc., the 801EJ is designed to be a layer below YAG (Ce) by phase separation. According to the present invention, L
The primary light emitted from the ED 11 is wavelength-converted only by the phosphor 18 and converted into blue light. The phosphor 17 is L
The wavelength of ultraviolet light emitted from the ED 11 is not substantially converted. With this feature, an extremely stable white balance can be obtained.

Here, it is assumed that both the phosphor 17 and the phosphor 18 convert the wavelength of the ultraviolet light emitted from the LED 11, respectively. In such a case, as described above with reference to FIG. 6, when the emission wavelength of the LED 11 changes, there arises a problem that the white balance changes. This is because it is almost impossible technically to make the wavelength dependences of the absorption rates of the phosphor 17 and the phosphor 18 the same.
As a result of the difference between the two absorption spectra, LED 11
When the wavelength of the primary light emitted from the light source varies, the balance of the light components absorbed by the phosphors 17 and 18 changes, and the balance of the converted and emitted secondary light also changes. Because.

On the other hand, according to the present invention, the LED 1
The primary light emitted from 1 is converted in wavelength only by the phosphor 18 and converted into blue light. Phosphor 17 is LED1
The wavelength of the ultraviolet light emitted from 1 is not substantially converted. Due to various factors as described above with reference to FIG.
Does not change even if the emission wavelength of the blue light changes. Then, part of the blue light is converted into yellow light by the phosphor 17. That is, according to the present invention, the balance between the blue light and the yellow light emitted from the light emitting device to the outside depends only on the mixing ratio of the phosphor 17 and the phosphor 18, and the emission wavelength and emission intensity of the LED 11 It is extremely stable without dependence.

As described above, according to the present invention, both the blue light and the yellow light extracted outside have extremely stable wavelength spectra, and the white balance of the resulting white light is also extremely stable. .

When three color phosphors are used, precise adjustment of the blending ratio is required, and it is not easy to reproduce the white balance. However, according to the present invention, only two color phosphors are used. In that case, the adjustment of the mixing ratio of the phosphor is much easier.

As the ultraviolet light emitting LED 11 that can be used in the present invention, indium aluminum gallium nitride In _x Al _y Ga _1-xy N (0 ≦ x <1, 0 ≦ y
A nitride semiconductor light-emitting device having <1) as an active layer can be mentioned.

[0026] Note that the term "nitride semiconductor" in the present _{application, B x In y Al z Ga} (1-xyz) N (O ≦ x ≦ 1, O ≦
y ≦ 1, O ≦ z ≦ 1) including a III-V compound semiconductor, and as a V-group element, phosphorus (P) in addition to N
It also includes mixed crystals containing arsenic (As) or arsenic.

FIG. 2 is a schematic sectional view showing a conceptual configuration of the semiconductor light emitting device. The laminated structure of the light emitting device of FIG. Note that the doping material, the film thickness, and the like may be appropriately changed as needed. (1) Sapphire substrate 131 (2) GaN buffer layer 132 (3) n-type GaN contact layer 133 having a thickness of 4 μm (4) n-type AlGaN cladding layer 13 having a thickness of 200 μm
4 (5) InGaN active layer 135 having a thickness of 50 μm. Here, the active layer may be doped, or the active layer may be a multilayer film such as a multiple quantum well (MQW). (6) 200 μm-thick p-type AlGaN cladding layer 13
6 (7) 50 μm-thick p-type GaN contact layer 137 The above-described laminated structure is partially etched from the surface to the n-type contact layer 133 as shown in FIG. ing. Further, a p-side electrode 143 having transparency is provided on the p-type contact layer 137. Further, bonding pads 142 and 144 are connected to the respective electrodes, and the surface of the element is covered with protective films 145 and 146.

The material of the substrate 131 is not limited to sapphire, and may be, for example, spinel, MgO,
ScAlMgO ₄ , LaSrGaO ₄ , (LaSr) (A
lTa) Insulating substrate such as O ₃ , SiC, Si, Ga
Each effect can be obtained by using a conductive substrate such as As or GaN in the same manner. Here, ScAlMgO ₄
In the case of a substrate, the (0001) plane, (LaSr) (Al
Ta) In the case of an O ₃ substrate, it is desirable to use the (111) plane.

The LED 11 illustrated in FIG.
When the composition of indium (In) 5 in the group III element is about 2 to 3%, ultraviolet light having a wavelength of about 370 to 375 nm is emitted with high emission intensity. LE like this
A white light emitting device combining D, a blue light emitting phosphor excited by ultraviolet light, and a yellow light emitting phosphor excited by blue light is extremely excellent in uniformity and stability of white balance. That is, since the emission wavelength of the phosphor is constant regardless of the intensity and wavelength of the light that excites the phosphor, the wavelength of the light emitting device is constant even if the characteristics of the semiconductor light emitting elements vary. Therefore, variations in white balance due to elements, variations in white balance due to current and temperature, and changes in white balance due to deterioration of elements do not occur.

Here, in the light emitting device illustrated in FIG. 1, in order to prevent the ultraviolet light emitted from the light emitting element 11 from leaking outside, the sealing resin 13 is made of a material having a high absorptivity to the ultraviolet light. It is desirable to be constituted by.

In this embodiment, a white light emitting device using an ultraviolet light emitting semiconductor light emitting element, a blue light emitting phosphor excited by ultraviolet light, and a yellow light emitting phosphor excited by blue light is specifically described. Although given as an example, the present invention is not limited to this. That is, the present invention provides a light-emitting element, a first phosphor that emits light when excited by light from the light-emitting element, a second phosphor that emits light when excited by light from the first phosphor, The same effect can be obtained by applying to all light emitting devices having

For example, a light-emitting semiconductor light-emitting element that emits light in a violet wavelength band as a light-emitting element, a blue-green light-emitting phosphor excited by purple light as a first phosphor, and blue-green light as a second phosphor In a light emitting device using each of the excited red light emitting phosphors, extremely uniform and stable white light can be obtained. Further, the light emitting element used in the present invention does not necessarily need to be a semiconductor light emitting element. That is, in addition to a semiconductor light emitting element such as an LED or a semiconductor laser, an EL (electro-luminescent) element or other various light emitting elements may be used.

Furthermore, the same curing can be obtained by applying the same method to a light emitting device that emits light other than white light. That is, the first phosphor that emits light when excited by light from the light emitting element and the second phosphor that emits light when excited by light from the first phosphor emits light with no change in chromaticity coordinates. The device can be realized.

Next, a second embodiment of the present invention will be described. FIG. 3 is a schematic sectional view illustrating a light emitting device according to the second embodiment of the present invention. That is, the light emitting device shown in FIG. 1 is generally called an SMD (Surface Mounted Device) lamp. That is, the wiring pattern 26 is formed on the surface of the mounting substrate 25, and the semiconductor light emitting element 11 is mounted thereon. The light emitting element 11 is appropriately connected to a wiring pattern 26 by a wire 24. The semiconductor light emitting device 11 is a light emitting device that emits light in the ultraviolet region.

The phosphors used in this embodiment are a blue light emitting phosphor 28 excited by ultraviolet light and a yellow light emitting phosphor 27 excited by blue light. In the figure, reference numeral 22 denotes a resin, a yellow light emitting phosphor 27 excited by blue light is applied on the resin, and a blue light emitting phosphor 28 excited by ultraviolet light is further applied thereon. . Further, the periphery thereof is sealed with a sealing resin 23. The inner resin 22 is formed of a material that absorbs less ultraviolet light.

In this embodiment, the blue light emitting phosphor 2
The yellow light emitting phosphor 27 is provided closer to the light emitting element 11 than the light emitting element 8. In such an arrangement, the ultraviolet light emitted from the light emitting element 11 is transmitted through the blue light emitting phosphor 28 without being absorbed by the yellow light emitting phosphor 27.
And is absorbed and converted into blue light. Then, of the blue light, the component emitted toward the inside of the light emitting device is absorbed by the yellow light emitting phosphor 27 and converted into yellow light. That is, also in the present embodiment, white light composed of blue light and yellow light can be extracted outside. Further, the white balance depends only on the ratio between the phosphors 27 and 28 and is not influenced by the fluctuation of the emission wavelength or the emission intensity of the light emitting element 11, as described in the first embodiment. . As a result, extremely stable and uniform white light can be obtained.

As examples of the phosphors 27 and 28 that can be used in the present embodiment, those similar to those described above with reference to the first embodiment can be given. That is, as the blue light emitting phosphor 28 excited by ultraviolet light, there is the aforementioned model 801EJ manufactured by Toshiba. In addition, 8
The specific gravity of 01EJ is 4.2. The yellow light-emitting phosphor 27 excited by blue light is YAG (Ce).
That is, (Y _1-a Gd _a ) ₃ (Al _1-b G _ab ) ₅ O ₁₂ : Ce
There is. Here, YAG (Ce) has an absorptance peak in the wavelength region of blue light. That is, while the absorptance for blue light is extremely high, the absorptance for light in the ultraviolet region emitted from the light emitting element 11 is extremely low. Therefore,
The primary light emitted from the light emitting element 11 is a yellow phosphor 27
Are not substantially absorbed, but pass through to reach the blue phosphor 28.

The method of applying these phosphors 27 and 28 can be the same as that described in the first embodiment. That is: (1) Cast YAG (Ce). That is, the phosphor is dispersed in a solvent, applied to the surface of the resin 22, heated, cured and cured. Thus, a layer of the blue phosphor 27 can be formed. Next, similarly, 801EJ is cast thereon. This series of methods can be used irrespective of the magnitude of the specific gravity of the phosphor. (2) A solvent in which 801EJ is dissolved and a solvent in which YAG (Ce) is dissolved are dropped on the surface of the resin 12. At this time, in consideration of the specific gravity of the phosphor particles, the viscosity and the curing speed of the solvent, the layer is designed so that YAG (Ce) becomes a layer lower than 801EJ by phase separation.

Next, a third embodiment of the present invention will be described. FIG. 4 is a schematic sectional view illustrating a light emitting device according to a third embodiment of the present invention. The light emitting device shown in the figure is also called a “vertical LED”. The present embodiment is characterized in that a phosphor is applied to the surface of the light emitting element 11.

That is, the ultraviolet light emitting element 11 is mounted on the cup portion of the lead frame 36 by the adhesive 30. On the surface of the light emitting element 11, a blue light emitting phosphor 38 excited by ultraviolet light is applied, and further thereon, a yellow light emitting phosphor 37 excited by blue light is applied.

Also in this embodiment, the blue light emitting phosphor 28 is excited by the ultraviolet light emitted from the light emitting element 11 to emit blue light, and a part of the blue light is absorbed by the yellow light emitting phosphor 27. Converted to yellow light. Then, white light composed of blue light and yellow light can be extracted.

In this embodiment, the phosphors 37 and 38 are used.
Is applied directly to the surface of the light emitting element 11, the wavelength can be converted in the vicinity of the light emitting element 11, and white light with high emission luminance can be obtained. Further, since the emission source of the white light can be made closer to the point light source, light having a predetermined radiation shape can be easily obtained by optical means. For example, by forming the resin 33 into a lens shape, parallel rays can be easily formed.

In the present embodiment, the light emitting element 1
Since there is no resin between 1 and the phosphors 37 and 38,
The absorption loss of ultraviolet light by such a resin can be eliminated. In addition, since many phosphors generally have an insulating property, there is no fear that an electrical short circuit occurs even when the phosphor is directly applied to the surface of the light emitting element 11 as in the present embodiment. The materials of the blue phosphor 38 and the yellow phosphor 37 used in the present embodiment and the method of applying the same can be the same as those in the above-described embodiments, and thus detailed description is omitted.

The order of applying the phosphors is reversed from that illustrated in FIG. 4. First, a yellow phosphor is applied to the surface of the light emitting element 11, and then a blue phosphor is applied thereon. good.

Next, a fourth embodiment of the present invention will be described. FIG. 5 is a schematic sectional view illustrating a light emitting device according to a fourth embodiment of the present invention. The light emitting device shown in FIG.
This is generally called a “seven-segment display”. In the figure, reference numeral 11 denotes an ultraviolet light emitting semiconductor light emitting device, which is mounted on a substrate 45. A blue light-emitting phosphor 48 excited by ultraviolet light and a yellow light-emitting phosphor 47 excited by blue light are mixed and applied on the element 11. 49 is a shielding member, and 43 is a sealing resin. In this embodiment, there is an advantage that it is not necessary to consider the absorption of ultraviolet light by the resin 43. In FIG. 5, electrode patterns and wires for wiring are omitted for convenience.

Even when the blue light-emitting phosphor 47 and the yellow light-emitting phosphor 48 are mixed and used as in this embodiment, the same effects as those of the above-described embodiments can be obtained. When phosphors of three colors are used as in a conventional light emitting device, separation occurs when the solvent is cured due to a difference in specific gravity of the phosphors, resulting in non-uniform coloring. On the other hand, when only two color phosphors are mixed as in the present embodiment, separation when the solvent is hardly occurs, and non-uniform coloring hardly occurs. In particular, when the specific gravity of the phosphor 47 is the same as that of the phosphor 48, for example, when 801EJ is used as the blue light-emitting phosphor 48 and YAG (Ce) is used as the yellow light-emitting phosphor 47, the separation is suppressed and extremely. This is effective in that uniform coloring can be easily obtained.

The embodiment of the invention has been described with reference to examples. However, the present invention is not limited to these specific examples. That is, the present invention provides a light-emitting element, a first phosphor that wavelength-converts light emitted from the light-emitting element, and light that does not substantially absorb light from the light-emitting element and emits light from the first phosphor. A light emitting device provided with a second phosphor that converts the emitted secondary light into a wavelength has the same function and effect, and the specific configuration of each element is appropriately determined by those skilled in the art. It can be selectively implemented.

Further, in each of the specific examples described above,
Although the description has been given of the case where the phosphors are provided, three or more phosphors may be used. For example,
A first phosphor that converts primary light from a light emitting element into secondary light, and a second phosphor that converts the wavelength of the secondary light to have different wavelengths.
A second phosphor and a third phosphor that emit the next light may be provided.

[0049]

The present invention is embodied in the form described above, and has the following effects.

That is, according to the present invention, a light emitting element that emits primary light of a first wavelength and a first phosphor that absorbs the primary light and emits secondary light of a second wavelength And the second
A second phosphor that absorbs secondary light having a wavelength of and emits secondary light having a third wavelength, wherein the second phosphor has a low absorptance for the first wavelength and is substantially By not configuring the wavelength conversion, the balance of the obtained optical spectrum is extremely stabilized,
Even if the wavelength or intensity of the next light changes, the change in the obtained light spectrum is eliminated.

For example, a case where white light is obtained using a semiconductor light emitting element having ultraviolet light emission, a blue light emitting phosphor excited by ultraviolet light, and a yellow light emitting phosphor excited by blue light will be described as an example. Has the following advantages. (1) Variations in the mounted light emitting elements, that is, variations in white balance due to individual differences are eliminated. (2) A change in white balance due to a change in current is eliminated. (3) Changes in white balance due to changes in temperature are eliminated. (4) Changes in white balance due to deterioration of the mounted light emitting element are eliminated.

In addition, as a method of emitting white light using fluorescence, the use of only two colors of phosphors has the advantage that (5) the mixing ratio of the phosphors can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a conceptual configuration of a light emitting device according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view illustrating a conceptual configuration of a semiconductor light emitting element used in the light emitting device of the present invention.

FIG. 3 is a schematic sectional view illustrating a light emitting device according to a second embodiment of the present invention.

FIG. 4 is a schematic sectional view illustrating a light emitting device according to a third embodiment of the present invention.

FIG. 5 is a schematic sectional view illustrating a light emitting device according to a fourth embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view illustrating a conceptual configuration of a conventional white light emitting type light emitting device.

[Explanation of symbols]

Reference Signs List 11 light emitting element 12, 22 resin 13, 23, 33, 43 sealing resin 14, 24, 34 wire 15, 36 lead frame 16, 36 lead frame 17, 27, 37, 47 yellow light emitting phosphor excited by blue light emission 18, 28, 38, 48 Blue phosphor 25 Substrate 26 Wiring pattern 30 Adhesive 22 Resin 23 Resin mold 24 Lead frame 25 Metal post 26 Metal stem 27 Yellow light-emitting phosphor excited by blue light 28 Excited by ultraviolet light Blue light-emitting phosphor 45 Substrate 49 Light-blocking member 111 Light-emitting element 112 Resin 113 Sealing resin 114 Wire 115, 116 Lead frame 117 Yellow phosphor 131 Sapphire substrate 132 GaN buffer layer 133 n-type GaN layer 134 n-type AlGaN layer 135 Active layer 136 p-type AlGa Layer 137 p-type GaN layer 141 n-side electrode 142 bonding pad 143 p-side electrode 144 bonding pad 145 SiO ₂ protective film 146 SiO ₂ protective film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideto Sugawara 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Pref. 7F-1 Toshiba Electronic Engineering Corporation F-term (reference) 5F041 AA11 AA12 CA40 EE25

Claims (5)

[Claims] A light-emitting element that emits light of a first wavelength; a first wavelength conversion means that absorbs light of the first wavelength and emits light of a second wavelength; A second wavelength conversion unit that absorbs light of a wavelength and emits light of a third wavelength. 2. The second wavelength is longer than the first wavelength, the third wavelength is longer than the second wavelength, and the second wavelength converting means is a first wavelength converter. The light-emitting device according to claim 1, wherein the light-emitting device does not substantially absorb light having a wavelength. 3. The light emitting device according to claim 1, wherein said first wavelength conversion means is a phosphor, and said second wavelength conversion means is a phosphor. 4. The light of the first wavelength is ultraviolet light, the light of the second wavelength is blue light, and the light of the third wavelength is yellow light. The light emitting device according to claim 1. 5. The light emitting device according to claim 1, wherein said light emitting element is a semiconductor light emitting element made of a nitride semiconductor.