Light emitting device

Light-emitting device

Technical field

The present invention relates to a light-emitting device including a light-emitting element, and more particularly to a light-emitting device. The light-emitting device includes: a light-emitting element capable of emitting light in a first spectral region; and a phosphor, which is derived from the alkaline earth metal orthosilicate group and It contains at least a phosphorous alkaline earth metal orthosilicate, and absorbs part of the light emitted from the light-emitting element and emits light in another spectral region.

Background technique

The light emitting device is, for example, an inorganic LED, an organic LED, a laser diode, an inorganic thick film electroluminescent sheet, or an inorganic thin film electroluminescent unit.

In particular, the salient features of LEDs are their long lifespan, no need for a large space, strong impact resistance, and the ability to emit light in a narrow spectral band.

The inherent light emission of the active semiconductor material LED cannot sufficiently provide many luminous colors, especially many luminous colors with broad spectral bands. This is especially true when the target is white light emission.

Judging from the prior art, the luminous colors that were not initially available from semiconductors can be obtained through color conversion technology.

The color conversion technology is basically based on the following principle: that is, at least one phosphor is placed on the LED mold; the phosphor absorbs the light emitted from the mold; then the phosphor emits photoluminescence light in another light emission color .

In order to compose the phosphor, basically, an organic material or an inorganic material can be used. The basic advantage of inorganic pigments is higher environmental resistance than organic substrate phosphors. Considering the long-life color stability based on inorganic LEDs, inorganic materials are more advantageous.

Considering the ease of processing, it is obvious that it is advantageous to use inorganic fluorescent pigments to replace organic fluorescent coated substrate phosphors, which require an excessively long growth period in order to obtain the necessary film thickness. The pigment is added to the matrix and then placed on the LED mold.

Due to the small number of inorganic materials that meet the above requirements, in most cases, YAG family materials are currently used as color conversion pigments. However, the disadvantage of YAG family materials is that they only have higher efficiency when the maximum light emission is less than 560nm. For this reason, when YAG pigments are used in combination with blue diodes (450nm and 490nm), only a cool white emission color can be achieved. In particular, in lighting equipment, the requirements regarding color temperature and color reproduction are very high. This requirement cannot be met by existing white LED products.

International Publication No. WO00/33389 discloses that Ba2SiO4:Eu2+ can be used as a phosphor to obtain light close to white when a blue LED is used. The light emitted by Ba2SiO4:Eu2+ has a relatively short wavelength of 505nm, so the light is obviously cool.

SHMPoort et al., "Optical properties of Eu2+-activated", page 297 reported the properties of Ba2SiO4 and a phosphate activated by Eu2+ such as KbaPO4 and KSrPO4. In this report, it is proved that the light emission of Ba2SiO4 is 505nm. Moreover, it is reported that the light emission of two phosphates is substantially shorter wavelengths (420nm and 430nm).

Summary of the invention

The object of the present invention is to provide a light emitting device that has excellent absorption of ultraviolet or blue rays emitted by the first light source through phosphors, and the light emitting device can provide different luminous colors or higher light emission through high photoluminescence. The color reproducibility. In this case, it is particularly advantageous that the color position of the color in the CIE slanted ellipse, which is generally used as the light source of general lighting equipment, is extremely close to the color temperature range between 2600K and 7000K.

According to the present invention, the light-emitting device includes: a light-emitting diode made of a nitride semiconductor; and a phosphor that absorbs a part of the light emitted by the light-emitting diode and emits light having a different wavelength from the absorbed light. The phosphor is made of an alkaline earth metal silicate fluorescent material activated with europium.

The phosphor can be an alkaline earth metal orthosilicate activated by divalent europium, which can be expressed as follows: (2-xy)SrOx(Ba,Ca)O·(1-abcd)SiO2·aP2O5bAl2O3cB2O3dGeO2:yEu2+ (where 0< x<1.6, 0.005<y<0.5, and 0<a, b, c, d<0.5) and/or alkaline earth metal orthosilicate can be represented by the following formula: (2-xy)BaO·x(Sr, Ca) O·(1-abcd)SiO2·aP2O5bAl2O3cB2O3dGeO2:yEu2+

(Wherein, 0.01<x<1.6, 0.005<y<0.5, and 0<a, b, c, d<0.5) Wherein, it is advantageous that at least one of a, b, c, and d is greater than 0.01.

That is, in the case of strontium silicate or a mixture of barium silicate and strontium orthosilicate instead of barium silicate, it was unexpectedly found that the wavelength of the radiated light was extended. The replacement of silicon by germanium and additional P2O3, Al2O3, and/or B2O3 can affect the light emission spectrum. As a result, the light emission spectrum can be adjusted to the best in each use situation.

Advantageously, the light-emitting device has phosphors from the alkaline earth metal aluminate family activated by divalent europium and/or manganese, and/or Y(V, P, Si)O4:Eu, or from alkaline earth metal disilicate Magnesium Eu2+ and Mn2+ are different phosphors used to emit red light, which can be represented by the following formula: Me(3-xy)MgSi2O3: xEu, yMn (wherein 0.005<x<0.5, 0.005<x<0.5, and Me represents Ba and /Or Sr and/or Ca).

Moreover, it has also been found that the inclusion of a small amount of monovalent ions in the phosphor matrix, especially halides, is beneficial to improve crystallinity and emissivity.

Advantageously, the first spectral region is 300 to 500 nm. In this wavelength region, the phosphor of the present invention can be well activated.

Moreover, it is advantageous that the second spectral region is 430 to 650 nm. In this case, relatively pure white light can also be obtained.

Advantageously, the light emitting device emits white light with an Ra value> 72.

Brief Description of the Drawings Fig. 1 shows a cross-sectional view of an LED lamp according to a second preferred embodiment of the present invention; Fig. 2 shows a cross-sectional view of the layered structure of the blue LED of Fig. 1; Fig. 3 shows a cross-sectional view of the layered structure of the blue LED in Fig. 1; The structure of the planar light source device according to the third preferred embodiment of the invention, wherein Figure 3 (a) is a plan view and Figure 3 (b) is a cross-sectional view along the line AA of Figure 3 (a); Figure 4 shows the present invention A cross-sectional view of the SMD (Surface Mount Diode) type LED lamp of the fourth preferred embodiment; FIG. 5 shows a cross-sectional view of the LED lamp according to the fifth preferred embodiment of the present invention; Fig. 7 shows a connection circuit diagram of a capacitor used as an overvoltage protection element; and Fig. 8 shows a cross-sectional view of a semiconductor light emitting device according to a sixth preferred embodiment of the present invention.

detailed description

In the first embodiment according to the present invention, the light emitting device includes two different phosphors, and in this case, at least one of the phosphors is an alkaline earth metal orthosilicate phosphor. Therefore, the white tone can be adjusted particularly accurately.

In the structural changes of the light emitting device according to the present invention, there are many possibilities. According to a preferred embodiment, one or more LED chips are arranged on a substrate in the reflector, and phosphors are dispersed in a lens arranged on the reflector.

However, it is also possible that one or more LED chips are arranged on the substrate in the reflector, and the phosphor is coated on the reflector.

The LED chip can be easily filled with a transparent dome-like sealant. On the one hand, the sealant provides mechanical protection, and on the other hand, the sealant also improves the optical performance (improves the light emission of the LED mold).

The phosphor can be dispersed in the sealant. Using the sealant, the LED chip and the polymer lens provided on the substrate can be bonded while containing as little gas as possible. In this case, the difference between the refractive index of the polymer lens and the sealant is at most 0.1. The LED mold can be directly sealed with a sealant. However, it is also possible to seal the LED mold with a transparent sealant (that is, in this case, a transparent sealant and a phosphor-containing sealant). Since the refractive indexes are close to each other, the refractive loss at the interface is small.

Advantageously, the polymer lens has spherical and elliptical depressions. The depression can be filled with a sealant. As a result, the LED array can be fixed at a short distance from the polymer lens. Therefore, the size of the mechanical structure can be reduced.

In order to achieve a uniform distribution of the phosphor, it is advantageous that the phosphor is conveniently suspended in the inorganic matrix.

In the case of using two kinds of phosphors, it is advantageous that the two kinds of phosphors are suspended in either matrix, and, in this case, these matrixes are arranged in front and behind the light propagation direction. Therefore, compared with the case where different phosphors are mixed together and dispersed, the matrix concentration can be reduced.

Next, the important steps in the process of manufacturing the phosphor according to the first preferred embodiment of the present invention will be explained below.

In the process of producing silicate phosphor, according to the selected component ratio, the alkaline earth metal carbonate, silicon dioxide and europium oxide are thoroughly mixed in each stoichiometric amount as the starting materials, and used to produce the phosphor The conventional solid-state reaction can be converted into the required phosphor in reducing air at 1100°C and 1400°C. In this regard, it is advantageous to add a small amount of ammonium chloride or another halide (preferably less than 0.2 mole) to the reaction mixture in order to increase the degree of crystallinity. If necessary, part of the silicon can be replaced by germanium, boron, aluminum or phosphorus, or part of the europium can be replaced by manganese. This can be achieved by adding compounds in corresponding amounts of the various elements described above, which are decomposed by heating. In this case, keep the range of reaction conditions.

The resulting silicate emits light with a wavelength of 510 nm to 600 nm, and its half-bandwidth reaches 110 nm.

By using a phosphor selected from the above-mentioned phosphor family or a mixture of phosphors selected from the above-mentioned phosphor family, or a mixture of alkaline earth metal aluminate phosphors activated by divalent europium and/or manganese , There are different phosphors used to emit red light selected from Y(V, P, Si)O4:Eu2+, and conventional phosphors selected from the Y2O2S:Eu3+ family, which can be obtained with a certain color temperature and higher Color reproduction of the emitted light color. These examples are shown below.

T=2778K (464nm+Sr1.4Ba0.6SiO4:Eu2+); x=0.4619, y=0.4247, Ra=72, T=2950K (464nm+Sr1.4Ba0.6SiO4:Eu2+); x=0.4380, y=0.004, Ra=73, T=3497K (464nm+Sr1.6Ba0.4SiO4:Eu2+); x=0.4086, y=0.3996, Ra=74, T=4183K (464nm+Sr1.9Ba0.08Ca0.2SiO4:Eu2+); x= 0.3762, y=0.3873, Ra=75, T=6624K (464nm+Sr1.9Ba0.02Ca0.08SiO4:Eu2+); x=0.3101, y=0.3306, Ra=76, T=6385K(464nm+Sr1.6Ba0.4SiO4 :Eu2++Sr0.4Ba1.6SiO4:Eu2+); x = 0.3135, y = 0.3397, Ra = 82, T = 4216K (464nm + Sr1.9Ba0.08Ca0.02SiO4: Eu2+); x = 0.3710, y = 0.3696, Ra=82,3954K(464nm+Sr1.6Ba0.4SiO4:Eu2++Sr0.4Ba1.6SiO4:Eu2++YVO4:Eu3+); x=0.3756, y=0.3816, Ra=84, T=6489K(464nm+Sr1 .6Ba0.4SiO4: Eu2++Sr0.4Ba1.6SiO4: Eu2++ barium magnesium aluminate: Eu2-); x = 0.3115, y = 0.3390, Ra = 66, T = 5097K(464nm+Sr1.6Ba0.4(Si0. 08B0.02)O4:Eu2++Sr0.6Ba1.4SiO4:Eu2+); x=0.3423, y=0.3485, Ra=82, T=5084K(464nm+Sr1.6Ba0.4(Si0.08Ba0.02)O4: Eu2++Sr0.6Ba1.4SiO4: Eu2++ magnesium strontium aluminate: Eu2+); x = 0.3430, y = 0.3531, Ra = 83, T = 3369K (464nm + Sr1.4Ba0.6Si0.95Ge0.05O4:Eu2+); x=0.4134, y=0.3959, Ra=74, T=2787K (466nm+Sr1.4Ba0.6Si0.98P0.02O4.01: Eu2+); x=0.4630, y=0.4280, Ra=72, T= 2913K (464nm+Sr1.4Ba0.6Si0.98Al0.02O4:Eu2+); x=0.4425, y=0.050, Ra=73, in an advantageous embodiment according to the present invention, the color conversion can be performed as follows.

One or more LED chips are assembled on the substrate. The sealing material is directly arranged on the substrate to form a hemispherical or semi-elliptical shape (on the one hand, to protect the LED chip protection device, and on the other hand to emit the preferred emitted light generated in the LED chip). The sealing material may seal each film separately, or may form a common sealing material for all LED films. Therefore, the manufactured substrate is provided in the reflector or the reflector is provided on the LED chip.

A lens is installed on the reflector. On the one hand, the lens is used to protect the device, on the other hand, fluorescent pigments are mixed in the lens. Therefore, the lens gives the impression of opacity and yellow color. When passing through the optical components, the blue light (including ultraviolet light) that passes through the lens is converted into longer-wavelength light (yellow light). As a result, a white impression can also be obtained by mixing blue light and converted light (yellow light). For example, the waveguide effect loss generated between parallel plates can be reduced due to the opacity and dispersion characteristics of the lens. Moreover, with the mirror, only the initially adjusted light is controlled to enter the lens. As a result, the total reflection effect is reduced at the beginning.

Alternatively, the reflector may be provided on each LED chip, the reflector is filled in a dome shape, and the lens is provided above each reflector or the entire device.

In the production of light emitting devices for lighting, it is advantageous to use an LED array instead of a single LED. In another preferred embodiment of the present invention, color conversion is performed by directly assembling LED chips on a substrate formed LED array (described below).

Using an encapsulant (such as epoxy), the LED array can be bonded to a transparent polymer lens made of another material (such as PMMA). The materials of the polymer and the sealant are selected so as to have the refractive index as close as possible, that is, to have phase matching. The sealant is present in the largest spherical or elliptical depression of the polymer lens. The importance of the concave shape is if the color conversion substance is dispersed in the sealant. Therefore, according to the shape of the recess, it is possible to ensure that the light emission color is obtained regardless of the angle. In addition, the above-mentioned array may be filled with a transparent sealant, and the above-mentioned array may be bonded with the above-mentioned polymer lens using a sealant containing a color conversion substance.

For LEDs that use at least two different phosphors and have particularly preferred color reproducibility, it is advantageous to disperse and add the phosphors separately instead of dispersing the phosphors together in a matrix. This method is particularly applicable to compounds whose final light emission color is obtained through multiple color conversion processes. That is, the light emission color with the longest wavelength is produced by one light emission process. In this case, the light emission process proceeds as follows: that is, the first phosphor absorbs the light emission of the LED, the first phosphor performs light emission; the second phosphor absorbs the light emission of the first phosphor, and the second phosphor performs Light emission. In particular, for such a process, it is advantageous to disperse phosphors in the front and rear of the light propagation direction, because the concentration of phosphors can be reduced accordingly compared to the case where various phosphors are simply dispersed.

The present invention is not limited to the above-mentioned embodiment. Phosphors can be combined in polymer lenses (or other optical elements). The phosphor may be directly disposed on the LED mold, or may be disposed on the surface of the transparent sealant. Moreover, the phosphor can be combined in the matrix together with the dispersed particles. Therefore, precipitation from the matrix can be prevented and monochromatic light emission can be ensured.

The above-mentioned example of using a phosphor with a photo-induced effect in a light emitting diode (LED) lamp will be described in detail below.

Fig. 1 is a typical cross-sectional view of an LED lamp according to a second embodiment of the light emitting device of the present invention. The LED lamp shown in Fig. 1 is also a so-called "lens-type LED lamp." The blue LED 4 formed by GaN semiconductor is mounted on a metal stem 3 through a base 5, and the metal stem 3 forms a cup 10, which is used as a reflector for the LED The light emitted from the blue LED 4 is reflected above the lamp. One electrode of the blue LED 4 is connected to the lead frame 2 through a gold connecting wire 7, and the other electrode is connected to the lead frame 1 through a gold connecting wire 6. The inside of the cup 10 is filled with an internal resin 8 which serves as a coating member for fixing the blue LED 4. Furthermore, the lead frame 2 and the lead frame 1 provided with a metal stem 3 are covered with an outer resin 9 as an injection molded part. Therefore, the blue LED 4 is double-covered with the inner resin 8 and the outer resin 9. The metal stem 3 and the lead frame 1 are also called mount leads. The blue LED 4 will be described in detail below.

The internal resin 8 containing the phosphor 11 is filled in the cup 10 to a level below the level of the upper edge of the cup 10. When a plurality of LEDs are arranged close to each other in this way, this structure can prevent color mixing between the LEDs, and can use the LEDs to realize a flat display, so as to produce a high-definition image.

Regarding the internal resin 8, silicone resin or epoxy resin which becomes transparent when cured is used. The inner resin 8 includes a phosphor 11 mainly composed of an alkaline earth metal orthosilicate and/or alkaline earth metal orthosilicate activated by divalent europium. As described above, the phosphor 11 has a photoluminescence effect. In particular, the phosphor 11 absorbs the light emitted from the blue LED 4 and emits light having a different wavelength from the absorbed light.

As an alternative to silicone resin or epoxy resin, low-melting glass can be used as the internal resin 8. Low melting point glass has excellent moisture resistance, and at the same time, it can prevent harmful ions from entering the blue LED4. Moreover, the light emitted by the blue LED 4 can also pass through the low-melting glass without being absorbed by the glass. Therefore, it is not necessary to expect light absorption to emit light with higher intensity.

Also, the scattering material may be incorporated into the silicone resin or epoxy resin containing the phosphor 11 as the internal resin 8 or into the low melting point glass containing the phosphor 11 therein. The scattering material irregularly reflects the light emitted from the blue LED 4 so as to generate scattered light. Therefore, the light emitted from the blue LED 4 may be more suitable for the phosphor 11, so that the amount of light emitted from the phosphor 11 may be increased. There is no particular limitation on the scattering material, and any well-known material can be used.

As for the external resin 9, an epoxy resin that becomes transparent when cured can be used.

From the viewpoint of good operability, various resins such as epoxy resin can be used for the base 5. It is preferable that the resin used for the base 5 has adhesive properties, and in addition, from the viewpoint of avoiding a short circuit between the layers at the side even when the base 5 is pushed out toward the side of the small blue LED 4 In view of this, it is preferable that the resin used for the base 5 also has insulating properties.

The base 5 is formed of a transparent resin, so that the light emitted non-directionally from the blue LED 4 can pass through the transparent resin and be reflected from the reflector on the surface of the cup 10 to be emitted above the LED lamp. In particular, when the LED lamp is used as a white light source, the color of the base 5 may be white that does not hinder the white light.

The base 5 may include a phosphor 11. In the case of the LED lamp using the phosphor 11, the optical density is much higher than the case of the LED lamp not using the phosphor 11. In particular, since the light emitted from the blue LED 4 cannot pass through the phosphor 11, the light emitted from the blue LED 4 is reflected by the phosphor 11 disposed near the LED 4, and is again used as the light excited by the phosphor 11 It is also reflected by the reflector on the surface of the cup 10, and is further reflected due to the difference in refractive index between different parts of the LED lamp. Therefore, the light is locally densely restricted to the portion near the blue LED 4, resulting in a very high light density near the blue LED 4, which helps to emit high-brightness light from the LED lamp.

The blue LED 4 emits non-directional light, and the emitted light is also reflected from the surface of the cup 10. The light passes through the base 5, and therefore, the light density in the base 5 is high. Therefore, incorporating the phosphor 11 into the base 5 allows the light emitted from the blue LED to be reflected by the phosphor 11 contained in the base 5 and re-use as the light excited by the phosphor 11 contained in the base 5. It is launched undirected. Therefore, adding the phosphor 11 to the base 5 at the same time can also enhance the brightness of the light emitted by the LED lamp.

Furthermore, the base 5 may also be made of resin containing inorganic materials such as silver. Since resin such as epoxy resin is used for the base 5 and used as the internal resin 8, when the high-brightness LED lamp is used for a long time, the internal resin 8 or the base 5 forms a synthetic resin very close to the blue LED 4, which appears brown Or it is black and degraded, resulting in a decrease in luminous efficiency. In particular, the coloring of the portion of the base 5 close to the blue LED 4 significantly reduces the luminous efficiency. The base 5 is required not only to have light resistance (aging resistance) to the light emitted by the blue LED 4, but also to have characteristics such as viscosity and close contact. The problem of resin degradation caused by light can be solved by using a resin containing an inorganic material (such as silver) for the base 5. The base 5 meeting these performance requirements can be achieved by mixing silver paste and phosphor 11 with mount paste, coating the mixture on the metal stem 3 (metal stem 3) with a mounting device, and then applying the blue The LED 4 is bonded to the coating.

In addition to being made of epoxy resin containing silver, the base 5 may also be made of organic resin containing inorganic materials, such as silicone resin. The inorganic material contained in the base 5 should be able to be in close contact with the resin, that is, it should have good adhesion to the resin, and at the same time, it should not be degraded by the light emitted by the blue LED 4. In order to meet these requirements, at least one inorganic material is selected from silver, gold, aluminum, copper, aluminum oxide, silicon, titanium oxide, boron nitride, tin oxide, zinc oxide, and ITO, and incorporated into the resin. In particular, silver, gold, aluminum, copper, and the like can increase heat radiation and can conduct electricity, and therefore, can be applied to semiconductor devices that are expected to have electrical conductivity. Alumina, silicon, titanium oxide, boron nitride and the like have high aging resistance and can maintain the base 5 with high reflectivity. Inorganic materials can have various forms, such as spherical, needle-like, and flake-like, and can be specifically determined in consideration of, for example, dispersibility and electrical conductivity. In the base 5, heat radiation, electrical conductivity and the like can be adjusted to various levels by changing the content of inorganic materials in the resin. However, since adding an inorganic material to the resin will not cause significant degradation of the resin, but will reduce the viscosity and degradation, the content of the inorganic material is not less than 5% and not more than 80% in terms of weight. The weight content of the inorganic material is not less than 60% and not more than 80% degradation is better suited to prevent the degradation of the resin.

In this way, incorporating an inorganic material such as silver (which is not easily degraded when exposed to emitted light) into the blue LED 4 can suppress the degradation of the resin in the base 5 caused by light. Therefore, the incorporation of inorganic materials can reduce the discoloration area caused by degradation, can prevent the reduction of luminous efficiency, and can provide good adhesion (close contact). At the same time, the phosphor 11 is incorporated into the base 5 to further improve the brightness of the LED lamp.

In this way, it is possible to provide an LED lamp that can emit light with high brightness, and even after being used for a long time under high brightness, the luminous efficiency is only slightly reduced. Moreover, using a material with high thermal conductivity can stabilize the characteristics of the blue LED 4 and reduce irregular colors.

Fig. 2 shows the layered structure of the blue LED 4 of the LED lamp shown in Fig. 1. The blue LED 4 includes a transparent substrate, such as a sapphire substrate 41. For example, the buffer layer 42, the n-type contact layer 43, the n-type cladding layer 44, the MQW (multiple quantum well) active layer 45, the p-type cladding layer 46, and the p-type contact layer 47 in this order, for example, by MOCVD A nitride semiconductor layer is formed on the sapphire substrate 41. Therefore, the optically transparent electrode 50 is formed on the entire surface of the p-type contact layer 47, the p-electrode 48 is formed on a part of the optically transparent electrode 50, and the n-electrode 49 is formed on a part of the n-type contact layer 43. These layers can be formed by, for example, sputtering or vacuum deposition.

The buffer layer 42 may be formed of, for example, AlN, and the n-type contact layer 43 may be formed of, for example, GaN.

The n-type cladding layer 44 may be formed of, for example, AlyGa1-yN, where 0y<1, the p-type cladding layer 46 may be formed of, for example, AlxGa1-xN, where 0<x<1, and the p-type contact layer 47 may be formed of, for example, AlzGa1 -zN is formed, where 0z<1 and z<x. The band gap of the p-type cladding layer 46 is larger than the band gap of the n-type cladding layer 44. Each of the n-type cladding layer 44 and the p-type cladding layer 46 may have a single-component structure, or a structure in which the above-mentioned nitride semiconductor layer with a thickness of not more than 100 angstroms, each layer having a different composition from each other, is stacked on each other Another layer on top to provide a superlattice structure. When the thickness of the layer is not more than 100 angstroms, cracks or crystal defects of the layer can be prevented from occurring.

The MQW activation layer 45 is composed of a plurality of InGaN well layers and a plurality of GaN barrier layers. The thickness of the well layer and the barrier layer is not more than 100 angstroms, preferably 60 to 70 angstroms, so as to form a superlattice structure. Since InGaN crystal is softer than other aluminum-containing nitride semiconductors such as AlGaN, using InGaN in the layers constituting the active layer 45 can provide the advantage that all stacked nitride semiconductor layers are not easily cracked. The MQW activation layer 45 may also be composed of multiple InGaN well layers and multiple AlGaN barrier layers. Alternatively, the MQW activation layer 45 may be composed of a plurality of AlInGaN well layers and a plurality of AlInGaN barrier layers. In this case, the band gap energy of the barrier layer is made larger than the band gap energy of the well layer.

The reflective layer may be provided on the side of the sapphire substrate 41 starting from the MQW activation layer 45, for example, on the side of the n-type contact layer 43 that is close to the buffer layer 42. The reflective layer may also be disposed on the surface of the sapphire substrate 41 which is away from the MQW activation layer 45 stacked on the sapphire substrate 41. The reflective layer preferably has the largest reflection coefficient with respect to the light emitted by the activation layer 45, and the reflective layer may be formed of, for example, aluminum, or have a multilayer structure formed of a thin GaN layer. The arrangement of the reflective layer allows the light emitted from the active layer 45 to be reflected by the reflective layer, which can reduce the internal absorption of the light emitted by the active layer 45, increase the upward light output, and reduce the incidence of light on the base 5, thereby preventing Degradation of the base 5 caused by light.

The half-value width of the light emission wavelength of the blue LED 4 having the above structure is not more than 50 nm, preferably not more than 40 nm. The peak light emission wavelength of the blue LED 4 is in the range of 380 nm to 500 nm, such as 450 nm.

In the LED lamp having the above structure, when a voltage is applied between the lead frames 1 and 2, the blue LED 4 emits blue light with a wavelength of 450 nm. The blue light excites the phosphor 11 contained in the inner resin 8. The excited phosphor 11 emits yellow light with wavelengths of 560 and 570 nm, and the mixed light composed of blue and yellow light in the inner resin 8 is leaked through the outer resin 9 To the outside. In this case, the mixed light seen by the naked eye of a person is white, and as a result, the LED lamp looks like an LED lamp emitting white light. In particular, the phosphor 11 is excited by the blue light emitted by the blue LED 4 and emits yellow light, which has a complementary color relationship with blue and has a longer wavelength than blue. According to the present invention, the combination of a plurality of phosphors can produce light closer to pure white.

Fig. 3 shows the structure of a planar light source device related to a light emitting device according to a third preferred embodiment of the present invention, in which Fig. 3(a) is a plan view thereof and Fig. 3(b) is a cross-section along the line AA of Fig. 3(a) Figure.

The planar light source device shown in FIG. 3 can be used in a backlight device such as a liquid crystal panel. By illuminating the liquid crystal panel from the back, the characters or images on the liquid crystal panel that do not have luminous properties generate brightness or contrast, and the visibility of the characters or images can be improved. The planar light source device is equipped with and consists of the following elements.

That is, the planar light source device includes: a transparent and substantially rectangular light guide plate 70; a plurality of LEDs 4 arranged in an array and buried on one side of the light guide plate 70, and optically connected to the light guide plate 70; for reflecting light The light-reflecting shell 71 of the light guide plate 70 surrounds the other surface of the light guide plate 70 except for the light-emitting surface 70a and is fixed to the light guide plate 70; the light scattering pattern 73 includes a symmetrical and fine concave-convex pattern. The transparent film 74 is formed on the light reflecting surface 72 opposite to the light emitting surface 70a of the light guide plate 70; the transparent film 74 is fixed to the light guide plate 70 so as to cover the light emitting surface 70a and contains the phosphor 11 therein.

Also, each of the blue LEDs 4 is fixed to the light reflective housing 71 so that a driving voltage of a predetermined voltage is applied from a power source through a power supply device such as a connecting wire and a lead frame. The light scattering pattern 73 is provided for scattering the light emitted from the blue LEDs 4 inside the light guide plate 70.

In the planar light source device with this composition, when a driving voltage is applied to each blue LED 4, each blue LED 4 that is driven emits light. The emitted light propagates inside the light guide plate 70 in a predetermined direction and collides with the light scattering pattern 73 formed on the light reflection surface 72 to be reflected and scattered. The light passing film 74 is emitted as plane light from the light emitting surface 70a. When part of the light emitted from the blue LEDs 4 passes through the film 74, it is absorbed by the phosphor 11, and at the same time the wavelength of the light is converted for re-emission. According to the principle mentioned above, this will cause the color of the emitted light to be changed to a composite color of the mixed light, for example, white when viewed from the front of the film 74. Similarly, according to the planar light source device of the third preferred embodiment, the light emitted from the blue LEDs 4 is input to the light guide plate 70, and then, when the input light is reflected and is formed on the reflective surface 72 of the light guide plate 70 When the scattering pattern 73 is scattered, the input light is emitted from the reflective surface 70a to the film 74, where the light is partially absorbed by the phosphor 11, and at the same time, wavelength conversion is performed for re-emission. Therefore, using only the blue LEDs 4 without using LEDs having each of red, green, and blue as in the conventional case, it is possible to make the color of the emitted light white. Moreover, in this structure, due to the phosphor 11 and the blue LED 4 Without direct contact with each other, the degradation of the phosphor 11 can be suppressed for a long time, and therefore, the predetermined color tone of the planar light source can be maintained for a long time.

In addition, by changing the kind of the phosphor 11 contained in the film 74, it is possible to realize that the color of the emitted light is not only white, but also other colors. If the mounting structure of the film 74 is made easy to remove, and a plurality of types of films 74 are prepared, each of which includes different kinds of phosphors 11, only by changing the film 74, You can easily change the color tone of the plane light source.

Moreover, in addition to the method of including the phosphor 11 in the film 74, the phosphor 11 may be coated on the film 74. In this case, a similar method to the case where the phosphor is included in the film 74 can be obtained. effect.

Moreover, although the blue LED 4 is optically connected to the light guide plate 70 by being embedded in the light guide plate 70, in addition to this, it is also possible to bond the blue LED 4 to the end surface of the light guide plate 70, or use a light guide device such as an optical fiber. The light emitted by the blue LED 4 is guided to the end surface of the light guide plate 70, thereby realizing the optical connection between the blue LED 4 and the light guide plate 70. Moreover, the number of blue LED 4 used may be one.

Fig. 4 shows an SMD (Surface Mount Device) type LED lamp according to a fourth preferred embodiment of the light emitting device of the present invention.

The SMD-type LED lamp has a structure as described below. The metal frame is formed by a wiring pattern of two gold foils 81 and 82, which are covered on the two surfaces of the glass epoxy substrate 80 with insulating properties and are electrically isolated from each other. On the wiring patterns 81 and 82, a frame 83 having a plastic cup 83a is provided. The surface of the cup 83a constitutes a reflecting mirror, which reflects the light emitted from the blue LED 4. Wiring patterns 81 and 82 are asymmetrical. The upper surface of the wiring pattern 82 extends to the center of the bottom of the space formed by the frame 83, while the other wiring pattern 81 is only exposed to the bottom of the space formed by the frame 83.

The blue LED 4 is firmly bonded to the upper surface of the wiring structure 82 with an epoxy resin adhesive containing silver wires. The P-electrode and wiring pattern 82 of the blue LED 4 are connected by a gold connecting wire 6, and the n-electrode and the wiring pattern 81 of the blue LED 4 are connected by a gold connecting wire 7.

The inside of the space formed by the cup 83a of the frame 83 is filled with a sealing material 88, and the sealing material 88 becomes transparent after being bonded. The blue LED 4 is fixed by the sealing material 88. The sealing material 88 includes a phosphor 11 mainly composed of alkaline earth metal orthosilicate and/or alkaline earth metal orthosilicate activated by divalent europium. The sealing material 88 includes epoxy resin or silicone resin. The sealing material 88 containing the phosphor 11 may be filled into the entire space formed by the cup 83 a of the frame 83 or into a position below the upper edge of the frame 83.

At the same time, the sealing material 88 containing the phosphor 11 may also contain a scattering substance. These scattering materials can cause irregular reflection of the light emitted by the blue LED and change the light into scattered light. As a result, the light emitted from the blue LED 4 easily collides with the phosphor 11, and therefore, the amount of light emitted from the phosphor 11 can be increased. There is no particular limitation on the scattering material, and well-known scattering materials can be used.

In an SMD-type LED lamp having a similar composition, when a voltage is applied between wiring patterns 81 and 82, the blue LED 4 emits blue light with a wavelength of 450 nm. The blue light excites the phosphor 11 contained in the sealing material 88, and the excited phosphor 11 emits yellow light having a wavelength of 560 to 570 nm. The mixed light composed of blue light and yellow light in the sealing material passes through the sealing material 88 to reach the outside, and human eyes appear to be white light. As a result, the LED light seems to emit white light. That is, the phosphor 11 is excited by the light emitted by the blue LED 4 and emits yellow light, which has a complementary color relationship with blue light and has a longer wavelength than blue light. According to the present invention, by combining a variety of phosphors, white light close to pure white can be obtained.

Fig. 5 shows a schematic diagram of an LED lamp of a light emitting device according to a fifth preferred embodiment of the present invention. In this embodiment, the blue LED 4 is configured to be free from electrostatic overvoltage and similar phenomena, and is configured to add an overvoltage protection element 91 to the light source shown in FIG. 1.

As shown in FIG. 5, the over-voltage protection element 91 is made on a chip that is basically the same size as the blue LED 4, and the protection element is located between the blue LED 4 and the base 5. In this embodiment, the blue LED 4 is mounted in an inverted chip form different from that shown in FIG. 1, the reason for which will be described later. The overvoltage protection element 91 is provided with electrodes 92 and 93 for connecting the blue LED 4 and the lead frame 1. The electrode 92 is located at a position opposed to the p-electrode 48 shown in FIG. 2, and the electrode 93 is located at a position opposed to the n-electrode 49. Moreover, the formed electrode 93 extends to the side of the overvoltage protection element 91 so as to be easily connected to the connection wire 6. The electrodes 92 and 93 on the overvoltage protection element 91 are connected to the p-electrode 48 and the n-electrode 49 of the blue LED 4 through Au bumps 94a and 94b, respectively. The overvoltage protection element 91 may be a Zener diode or a capacitor or the like. The Zener diode starts to work when the applied voltage is greater than a prescribed voltage, and the capacitor absorbs the pulse voltage.

FIG. 6 shows a connection circuit diagram in which a Zener diode is used as the overvoltage protection element 91. The Zener diode 95 used as the overvoltage protection element 91 is electrically connected in parallel with the blue LED 4, wherein the anode of the blue LED 4 is connected to the cathode of the Zener diode 95. When an overvoltage is applied between the lead frame 1 and the lead frame 2 and if the voltage is greater than the Zener voltage of the Zener diode 95, the terminal voltage of the blue LED 4 is maintained by the Zener voltage, so that the voltage of the former does not exceed the Zener voltage. Nano voltage. Therefore, it is possible to prevent the application of overvoltage to the blue LED 4, so that the blue LED 4 is not affected by the overvoltage, thereby avoiding the LED 4 from equipment failure or performance degradation.

FIG. 7 shows a connection circuit diagram in which a capacitor is used as the overvoltage protection element 91. The capacitor 96 used for the overvoltage protection element 91 may be a chip-shaped element for surface mounting. The capacitor 96 having a structure as described above is provided with strip-shaped electrodes on its opposite sides, and these electrodes are connected in parallel to the anode and cathode of the blue LED 4. When an overvoltage is applied between the lead frame 1 and the lead frame 2, a charging current flows through the capacitor 96 due to the overvoltage to quickly reduce its terminal voltage. Therefore, the voltage applied to the blue LED 4 does not increase. Therefore, the blue LED 4 can be prevented from being affected by overvoltage.

Moreover, even when noise containing high-frequency components is applied, the capacitor 96 functions as a bypass capacitor, so additional noise can be eliminated.

As described above, the blue LED 4 is mounted in the form of an inverted chip, which is reversed with respect to the situation shown in FIG. 1. The reason is that because the overvoltage protection element 91 is provided, both the overvoltage protection element 91 and the blue LED need to be electrically connected. If each of the blue LED 4 and the overvoltage protection element 91 are connected using a connecting wire, the number of connecting wires is increased, thereby reducing productivity. In addition, due to the increase in contact and disconnection of the connecting wire itself, etc. , Thus there is a hidden danger of reduced reliability. Therefore, the blue LED is mounted in the form of an inverted chip. More specifically, the sapphire substrate 41 shown in FIG. 2 is located on the uppermost side, where the p-electrode 48 is connected to the electrode 92 of the overvoltage protection element 91 through the Au bump 94a, and the n-electrode 49 is through the Au bump. 94b is connected to the electrode 93 of the overvoltage protection element 91. Therefore, it is not necessary to connect the connecting wires 6 and 7 to the blue LED 4. If the blue LED 4 is mounted in the form of an inverted chip, the light-transmitting electrode 50 shown in FIG. 2 can be replaced by an opaque electrode. Furthermore, it may be arranged such that the n-electrode 49 is thickened so as to have the same height as the surface of the p-electrode 48, or the n-electrode 49 is connected with a new conductor so that it can be used as an electrode.

As described above, according to the structure shown in FIG. 5, in addition to the standard advantages of the light source structure shown in FIG. 1, it also has the following advantage that even if an overvoltage is applied due to static electricity or the like, the LED 4 will not occur. The situation is damaged or performance deteriorated. Moreover, since the overvoltage protection element 91 is used as a secondary base, even if the blue LED 4 is mounted in the form of an inverted chip, the height of the connection position of the connecting wires 6 and 7 on the side of the chip will not be reduced. Therefore, the connection is made at substantially the same position as the structure of FIG. 1.

If a semiconductor device is used as the overvoltage protection element 91 of FIGS. 5 and 6, a normal silicon diode can be used instead of the Zener diode. In this case, the number of silicon diodes is determined such that the polarities of multiple silicon diodes are made the same as each other, and they are connected in series with each other, so that the total forward voltage drop value (about 0.7 V×the number of silicon diodes) is equal to the operating voltage.

Moreover, a variable resistor can also be used for the overvoltage protection element 91. The characteristic of the variable resistor is that its resistance value decreases as the applied voltage increases. Therefore, like the Zener diode 95, the variable resistor can suppress overvoltage.

Fig. 8 shows a semiconductor light emitting device according to a sixth preferred embodiment of the present invention.

The semiconductor light-emitting device shown in FIG. 8 includes: lead frames 1, 2, metal stem 3, blue LED 4, base 5, connecting wires 6, 7, internal resin 8 without phosphor 11, external resin 9. A cup 10, and a transparent phosphor cover 100; wherein the light emitted from the light emitting element is wavelength-converted and radiated to the outside of the lens-shaped resin sealant.

Furthermore, the phosphor cover 100 is made of a resin coating material such as containing phosphor i1, and phosphorescence is generated when the phosphor 11 is excited by the light emitted from the blue LED 4. The resin coating material is, for example, transparent polyester resin, acrylic resin, urethane, nylon, silicone resin, vinyl chloride, polyethylene, phenolic plastic, CR39 (propylene glycol carbonate resin) and so on. Since urethane, nylon, and silicone can increase the elasticity of the phosphor cover 100, it is easy to install it on the outer resin 9.

Also, the phosphor cover 100 is shaped so as to be pasted on the outer surface of the outer resin 9, that is, shaped as a solid structure in which the hemispherical cover is integrated with the upper part of the cylindrical cover, and is detachably mounted on the outer resin 9. Moreover, the phosphor cover 100 is preferably a thin film in order to reduce light scattering caused by the phosphor 11. Also, when the resin containing the phosphor 11 is formed into a predetermined shape by injection molding and then pasted on the external resin 9, the phosphor cover 100 can be manufactured relatively easily. However, the phosphor cover 100 can be manufactured by directly spraying the resin material containing the phosphor 11 onto the external resin 9 and curing the resin material, so that no air gap occurs between the external resin 9 and the phosphor cover 100 .

In the semiconductor light emitting device with the above structure, light emitted from the blue LED 4 is incident into the phosphor cover 100 via the inner resin 8 and the outer resin 9. Part of the incident light is absorbed by the phosphor 11, and is emitted to the outside after being wavelength-converted at the same time. Therefore, the color of the emitted light viewed from the outside of the phosphor cover 100 is the color of the synthesized light, as white is formed according to the aforementioned principle.

Therefore, according to the sixth embodiment of the semiconductor light emitting device, since the inner resin 8 and the outer resin 9 as the resin sealant of the blue LED 4 do not contain the phosphor 11, the phosphor cover 100 for covering the outer resin 9 contains phosphorescence. Therefore, the light scattering caused by the phosphor 11 does not occur in the inner resin 8 and the outer resin 9. Moreover, since the phosphor cover 100 is formed into a thin film, the amount of light scattering due to the phosphor 11 is relatively small. Therefore, by molding the lens portion of the outer resin 9 into an arbitrary shape (a hemispherical shape in the present preferred embodiment), a desired light directivity can be obtained, so that the reduction in brightness accompanying wavelength conversion can be minimized.

In addition, by changing the kind of the phosphor 11 included in the coating material of the phosphor cover 100, emitted light of other colors than white light can be obtained. When the phosphor cover 100 has an easily detachable structure, and several kinds of phosphor covers 100 containing different kinds of phosphors 11 are prepared, the color tone of the emitted light can be easily changed by changing the phosphor cover 100.

Also, when the phosphor 11 is applied to the surface of the phosphor cover 100 instead of being included in the phosphor cover 100, a similar effect can be obtained. Moreover, since the phosphor cover 100 can be mounted on a semiconductor light emitting device available on the market, the semiconductor light emitting device can be manufactured at low cost.

As described above, the light emitting device including the light emitting element and the phosphor according to the present invention is suitable for LED displays, backlight devices, signal lights, lighting switches, various sensors, and various indicators.