JP2007070445A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device capable of obtaining emission spectra close to natural light, that is, good color rendering properties in a light emitting device using a semiconductor light emitting element and a phosphor. <P>SOLUTION: The light emitting device comprises a semiconductor light emitting element which emits excitation light and a plurality of phosphors which emit fluorescence by absorbing the excitation light. The elements composing the phosphor comprise Si, Al, O, N and lanthanoide rare-earth elements. The light emitting device excellent in color rendering properties is obtained by using a plurality of phosphors different in emission peak wavelengths due to a different ratio of the elements composing the plurality of phosphors. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting device using a phosphor, particularly an oxynitride phosphor and a semiconductor light emitting element.

  Semiconductor light-emitting elements such as light-emitting diodes (LEDs) have the advantage that they are small in size, consume less power, and can stably emit light with high brightness. Further, a light-emitting device that obtains visible light by combining a semiconductor light-emitting element and a phosphor has the advantages of a semiconductor light-emitting element and can emit light of a color such as white according to the purpose of use. It can be used as a light source for backlights such as telephones or portable information terminals, display devices used for indoor and outdoor advertisements, indicators for various portable devices, lighting switches, light sources for OA (office automation) devices, and the like.

  Patent Document 1 discloses a light-emitting device in which a semiconductor light-emitting element that emits blue or blue-violet light and one or two phosphors are combined. Here, the phosphor is selected so that the light emission color of the semiconductor light emitting element and the light emission color of the phosphor have a complementary color relationship to emit pseudo white light.

  In Patent Document 2, a group III nitride semiconductor that emits ultraviolet light having an emission peak wavelength of 380 nm is used as an excitation light source, and three types of phosphor layers that emit light of three primary colors of red, green, and blue, respectively. A dot matrix type display device is disclosed.

  Further, Patent Document 3 discloses a light-emitting device that emits white light using a semiconductor light-emitting element that emits light with a wavelength of 390 nm to 420 nm and a phosphor that is excited by light emission from the semiconductor light-emitting element. ing. Here, since the semiconductor light emitting element emits light with low human visibility, there is an advantage that the color tone hardly changes even if the light emission intensity or emission wavelength of the semiconductor light emitting element varies. In addition, light with a wavelength of 390 nm to 420 nm is less likely to damage device components such as a resin that disperses phosphors, and has little adverse effect on the human body.

  Conventionally, oxides and sulfides have been widely used as phosphor materials, but in recent years, examples of phosphors of oxynitrides and nitrides are disclosed in Patent Documents 4, 5, and 6 and Non-Patent Documents 1 and 2. Is disclosed. In particular, these phosphors can emit light with high efficiency when excited with light having a wavelength of 390 nm to 420 nm, have high chemical stability and heat resistance, and have little fluctuation in light emission efficiency due to changes in use temperature. Many have excellent properties such as.

Patent Document 7 discloses a light emitting device having the following configuration. Excited phosphor by the light emitting element of the wavelength of 400nm excitation _{(Ca 0.93, Eu 0.05, Mn} 0.02) 10 (PO 4) 6 Cl 2 to blue region from blue-violet phosphor (Ca _{0 .955} Ce _0.045 ) ₂ (Si _0.964 Al _0.036 ) ₅ N ₈ has an emission peak from blue-green to a green-based region, and phosphor SrCaSi ₅ N ₈ : Eu has a light-emitting peak from a yellow-red to a red-based region, respectively. Has a wavelength. It is said that the light emission color is exhibited in the white region due to the color mixture of light from these phosphors.

  Among the oxynitride phosphors, the JEM phase phosphor disclosed in Patent Document 6 is a silicon oxynitride fluorescence having a JEM phase that is a crystal phase different from α sialon (α phase) or β sialon (β phase). It is known that it exhibits a strong blue light emission that is unprecedented by excitation of near ultraviolet rays.

Although the efficiency of the blue phosphor has been improved in this way, it is necessary to increase the ratio of the blue phosphor because the visibility in blue is low. If the full width at half maximum of the emission spectrum of the blue phosphor is narrow, it is difficult to obtain good color rendering.
Japanese Patent Laid-Open No. 10-163535 JP-A-9-153644 JP 2002-171000 A JP 2002-363554 A JP 2003-206481 A International Publication No. 2005/019376 Pamphlet JP 2004-244560 A Naoto Hirosaki, Rong-Jun Xie, Koji Kimoto, Takashi Sekiguchi, Yoshinobu Yamamoto, Takayuki Suehiro, and Mamoru Mitomo, Characterization and properties of green-emitting β-SiAlON: Eu2 + powder phosphors for white light-emitting diodes, Applied Physics Letters 86, 211905 (2005) Ryota Ueda, Naoto Hirosaki, Akira Yamamoto, Hoei Army, “Red nitride phosphor for white LED”, 305th Phosphor Society Conference Preliminary Proceedings, 2004, p37-47

  For example, in order to realize a light-emitting device that emits white light using a semiconductor light-emitting element that emits light having a wavelength of 390 nm to 420 nm as an excitation light source, a plurality of phosphors such as blue, green, and red are usually required. However, since the emission spectrum obtained as a whole is one in which the emission peak wavelengths of the three types of phosphors are strong, the emission spectrum is not uniform, and therefore the color rendering properties are low.

  In addition, since it is necessary to use a blue phosphor with relatively low visibility and insufficient luminous efficiency, the amount of blue phosphor is larger than that of other phosphors. In the case of mixing, it is difficult to uniformly disperse in a medium such as resin, and as a result, variation in color tone has occurred.

  An object of the present invention is to provide a light emitting device capable of obtaining an emission spectrum close to natural light, that is, good color rendering.

  Hereinafter, means for solving the problems according to the present invention will be described. In addition, in order to explain the reason for using the means, some of the actions and effects associated with the means are also described, but these effects are not intended to solve the problem but are incidental. Therefore, the invention is not limited.

  The present invention is a light emitting device including a semiconductor light emitting element that emits excitation light and a plurality of phosphors that emit fluorescence by absorbing at least the excitation light, and each of the composition elements of the plurality of phosphors is at least Si, Al, O, N, and Re (Re is one element of a lanthanoid rare earth common to the plurality of phosphors), and the ratio of the composition elements in each of the plurality of phosphors is different. The light emitting device is characterized in that the emission peak wavelengths of the phosphors are different. As described above, by using a plurality of phosphors having substantially the same composition element type and different composition ratios, an effect similar to that obtained by using a single phosphor having an extremely wide emission spectrum full width at half maximum is obtained. It is done.

The present invention, in the plurality of phosphors, main crystal phase is JEM phase, expressed by a composition formula _{M 1-x Ce x Al (} Si y1-z Al z) N y2-z O z, wherein M is And at least one element selected from the group consisting of La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, wherein x is 0.1 ≦ x ≦ 1 Preferably, the light emitting device is characterized in that z is a real number satisfying 0.9 ≦ z ≦ 1.1, y1 is about 6, and y2 is about 10. The range of x is a value experimentally obtained as a range in which good luminous efficiency is obtained, and the range of z is a value obtained experimentally as a range in which a JEM phase is obtained.

  The present invention is preferably a light emitting device characterized in that the x values of the plurality of phosphors are different from each other. The present inventors have found that, in the JEM phase phosphor, the color tone can be changed by changing the composition formula x, that is, the Ce activation amount.

  The present invention is preferably a light emitting device, wherein the plurality of phosphors include a phosphor having x less than 0.5 and a phosphor having x of 0.5 or more.

  The light emitting device according to the present invention is preferably characterized in that the emission peak wavelengths of the plurality of phosphors are all 450 nm or more and 510 nm or less.

  The present invention is preferably a light emitting device characterized in that the full width at half maximum of the emission spectra of the plurality of phosphors is 80 nm or more.

  The present invention is preferably a light emitting device characterized in that the upper limit and the lower limit of the particle diameter of the plurality of phosphors are substantially the same.

  The light emitting device may further include a phosphor that absorbs the excitation light and emits green to yellow light.

  The present invention is preferably a light emitting device characterized in that the phosphor emitting green to yellow light is an oxynitride phosphor.

  In the present invention, it is preferable that the phosphor emitting green to yellow light is an Eu-activated α sialon phosphor.

  The light emitting device according to the present invention is preferably a light emitting device characterized in that an emission peak wavelength of the phosphor emitting green to yellow light is 510 nm or more and 605 nm or less.

  The present invention is preferably a light emitting device characterized in that the full width at half maximum of the emission spectrum of the phosphor emitting green to yellow light is 80 nm or more. Thereby, a light emitting device having excellent color rendering can be realized.

  The present invention is the light emitting device characterized in that the upper and lower limits of the particle size of the phosphor emitting green to yellow light are substantially the same as the upper and lower limits of the particle size of the plurality of phosphors. Is preferred. Accordingly, the plurality of phosphors and the phosphor emitting green to yellow light are uniformly dispersed in a dispersion material such as a resin, so that variation in chromaticity of the light emitting device can be suppressed.

  The light-emitting device may further include a phosphor that emits red light by absorbing the excitation light.

  The present invention is preferably a light emitting device characterized in that the phosphor emitting red light is an oxynitride phosphor or a nitride phosphor.

In the present invention, it is preferable that the phosphor emitting red light is Eu-activated CaSiAlN ₃ .

  The light emitting device according to the present invention is preferably a light emitting device characterized in that an emission peak wavelength of the phosphor emitting red light is 600 nm or more and 670 nm or less.

  The phosphor of the present invention preferably has a full width at half maximum of emission spectrum of the phosphor emitting red light of 80 nm or more. Thereby, a light emitting device having excellent color rendering can be realized.

  The present invention is preferably a light emitting device characterized in that the upper and lower limits of the particle size of the phosphor emitting red light are substantially the same as the upper and lower limits of the particle size of the plurality of phosphors. . As a result, since the particle size is similar to that of the plurality of phosphors, both types of phosphors can be uniformly dispersed.

  The present invention is preferably a light emitting device characterized in that an emission peak wavelength of the excitation light is 350 nm or more and 420 nm or less.

  In the present invention, the chromaticity coordinate x of light emission of the light emitting device is 0.22 or more and 0.44 or less, and the chromaticity coordinate y is 0.22 or more and 0.44 or less, or the light emission from the light emitting device. It is preferable that the light emitting device has a chromaticity coordinate x of 0.36 or more and 0.5 or less and a chromaticity coordinate y of 0.33 or more and 0.46 or less. If it is this chromaticity coordinate, since white or a light bulb color is obtained, it is especially suitable as a light-emitting device for illumination applications.

  The present invention uses a plurality of phosphors having substantially the same type of composition element and different emission peak wavelengths, so that an effect similar to that of effectively using one phosphor having a very wide emission spectrum full width at half maximum is obtained. Is obtained. Therefore, in particular, flattening of the emission spectrum from blue to blue-green, which has been difficult in the past, can be realized. Moreover, since these several fluorescent substance has similar specific gravity, it can disperse | distribute to resin etc. uniformly. By combining these phosphors with other phosphors that have a complementary relationship with the wavelength in the visible light region, a light emitting device that is white and has high color rendering can be realized.

  In the following, the best embodiments of the JEM phase phosphor and other phosphors, which are a plurality of phosphors that absorb ultraviolet to purple light and emit blue to blue-green light, are shown, and blue to blue green An example of a light-emitting device that emits light such as white light by combining a plurality of phosphors that emit light with other phosphors that emit visible light will be described.

(JEM phase phosphor)
The plurality of phosphors emitting blue to blue-green light are oxynitride phosphors (particularly, those containing silicon, aluminum, oxygen, nitrogen, and a lanthanoid element that is a luminescent center) and have a composition formula La _1-x A Ce ³⁺ activated JEM phase phosphor represented by Ce _x Al (Si _6-z Al _z ) N _10-z O _z was used.

  As a result of studying a JEM phase phosphor having excellent emission characteristics in the blue to blue-green region, the present inventors have found that light emission occurs when x (the activation amount of Ce) of the composition formula in the JEM phase phosphor is changed. It was found that a good phosphor with a wide emission spectrum full width at half maximum and high emission efficiency can be obtained in the blue to blue-green peak wavelength region. By mixing and using two kinds of this phosphor, it is possible to uniformly disperse the phosphor in a resin or the like. As a result, one kind of phosphor having a very wide emission spectrum full width at half maximum is obtained. It was found that light emission almost the same as that used was obtained.

FIG. 1 shows an excitation spectrum (fluorescence intensity when the wavelength of excitation light is changed) when x in the composition formula of the JEM phase phosphor is changed. For example, when x in the composition formula is 0.5, it can be seen that the excitation spectrum intensity is high near the wavelength of 380 nm. This is ^{presumably because the} absorption by Ce ³⁺ ions, which are the emission center, is strong in this wavelength region. FIG. 2 shows an emission spectrum measurement result when x in the composition formula is changed. However, light having a wavelength of 405 nm is used as excitation light. It has been found by the present inventors that the emission peak wavelength changes in the range from blue to blue-green by increasing x in the composition formula. In particular, when x = 0.1 in the composition formula, the emission peak wavelength is about 478 nm and the emission spectrum full width at half maximum is about 115 nm. When x = 1 in the composition formula, the emission peak wavelength is about 505 nm and the emission spectrum full width at half maximum. Is about 120 nm. As described above, since the full width at half maximum of the emission spectrum is very wide, a yellow component and a red component are included, and white light can be obtained only by using another phosphor that can compensate for the deviation from white. In addition, since the light emission increases as x in the composition formula, which is the activation amount of Ce, the value of x is suitably 0.1 or more and 1 or less. Further, from this, La contained in the composition ratio 1-x hardly contributes to light emission, and therefore, a lanthanoid element capable of substituting La with La, that is, La, Pr, Nd, Sm, Eu, It is possible to replace with at least one element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

  Among them, for the blue phosphors 11 and 13, the composition formula x = 0.1, that is, the La atom concentration was 4.95%, and the Ce atom concentration was 0.55%. For the blue-green phosphors 12 and 14, the composition formula x = 1.0, that is, the La atom concentration was 0%, and the Ce atom concentration was 5.5%. Further, z in the composition formula, which is a parameter for stably forming the JEM phase phosphor, is z = 1.05 for the blue phosphor 11 and the blue-green phosphor 12, and the blue phosphor 13 and the blue-green phosphor. 14 was set to z = 0.95. If the value of z is 0.8 or more and 1.2 or less, a JEM phase is obtained under normal production conditions, and if it is 0.9 or more and 1.1 or less, it is relatively easy regardless of the production conditions. A JEM phase is obtained.

  The blue and blue-green phosphors 11 to 14 are manufactured as follows. Silicon nitride powder having an average particle size of 0.5 μm, oxygen content of 0.93% by mass and α-type content of 92% was mixed with aluminum nitride powder, lanthanum oxide powder and cerium oxide powder. This mixed powder was put into a boron nitride crucible, and the crucible was introduced into an electric furnace of a graphite resistance heating system.

  The inside of the electric furnace was evacuated by a vacuum pump, and then heated from room temperature to 800 ° C. Here, nitrogen gas having a purity of 99.999% by volume was introduced and the pressure was set to 1 MPa. Furthermore, it baked by heating to 1700 degreeC at the speed of about 500 degreeC / hour, and hold | maintaining for 2 hours. After firing, the phosphor was taken out at room temperature. It has been confirmed that a JEM phase phosphor can be obtained if the nitrogen pressure is 0.5 MPa or more.

  In the sintered body fired by the above method, the ratio of the JEM phase in the crystal phase is determined by the X-ray diffraction method described in Patent Document 6 and the identification of the diffraction peak. The blue-green phosphor 12 was found to be the main component (50% or more) with 84% of the JEM phase.

  Here, the JEM phase is defined as a substance having a unique atomic occupation position (atomic arrangement structure) and a crystal structure (Pbcn space group) characterized by the coordinates as described in Table 1. .

  In Table 1, the symbol of the site is a symbol indicating the symmetry of the space group. Each coordinate of x, y, z indicates the position of the element in each lattice, and takes a value from 0 to 1. In the atom column, “RE” represents M (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, at least one element selected from the group consisting of ) And Ce enter with the respective composition ratio probabilities (1-x and x), “Al” contains only Al, and “M (1)” to “M (3)” contain Si and Al, respectively. The composition ratios (6-z and z) are entered, and “X (1)” to “X (5)” contain N and O with the respective composition ratio probabilities (10-z and z). By comparing the X-ray diffraction data calculated using the values in Table 1 with the X-ray diffraction results obtained by measurement, it is possible to identify whether the obtained material is in the JEM phase.

Incidentally, JEM phase phosphor of the composition formula _{La 1-x Ce x Al (} Si y1-z Al z) in _{N y2-z O} z, be a y1 = 6, y2 = 10 if an ideal JEM phase However, since a glass phase and other crystal phases may actually be mixed, the result of the composition analysis slightly deviates from the expected value. For example, y2 is about 5.9 to 6.1, and y2 is about 10.0 to 10.7.

(Yellow phosphor)
As the yellow phosphor 20, a composition formula Ca _0.93 Eu _0.07 Si ₉ Al ₃ ON which is an oxynitride phosphor (especially, containing silicon, aluminum, oxygen, nitrogen, and a lanthanoid element which is a light emission center). _{As the 15} α sialon phosphor and the yellow phosphor 21, an α sialon phosphor having a composition formula (Ca _0.93 Eu _0.07 ) _0.25 Si _11.25 Al _0.75 ON _15.75 was used.

  The yellow phosphor 20 has the characteristics that the emission peak wavelength is about 590 nm and the emission spectrum full width at half maximum is as wide as about 90 nm or more. Further, the yellow phosphor 21 has an emission peak wavelength of about 580 nm and an emission spectrum full width at half maximum of about 90 nm. In both phosphors, the excitation spectrum has a strong peak in the ultraviolet to violet region.

  The yellow phosphors 20 and 21 are produced as follows. Eu activation that emits yellow light by mixing silicon nitride, aluminum nitride, calcium carbonate, europium oxide powder, then putting it in a boron nitride crucible, reacting in nitrogen at 1 MPa at 1800 ° C. for 10 hours, and then grinding. An α sialon phosphor is produced.

(Red phosphor)
The red phosphor 30 is a nitride phosphor (especially, containing silicon, aluminum, nitrogen, and a lanthanoid element that is a light emission center), and is described in Non-Patent Document 2. CaAlSiN ₃ : Eu ³⁺ (Eu activation) Amount 0.8%) was used. This is produced as follows. Silicon nitride, aluminum nitride, calcium nitride and europium nitride powder are mixed in a glove box where moisture and air are blocked, then placed in a boron nitride crucible, reacted at 1 MPa in nitrogen at 1800 ° C., and then pulverized Thus, a CaAlSiN ₃ phosphor activated with Eu is produced.

  The red phosphor 30 has the characteristics that the emission peak wavelength is about 650 nm and the full width at half maximum of the emission spectrum is as wide as about 90 nm or more.

(Semiconductor light emitting device)
The semiconductor light emitting device 64 is made of a GaN-based semiconductor (a semiconductor containing at least Ga and N, and optionally using Al, In, an n-type dopant, a p-type dopant, etc.), and the active layer is an InGaN-based material. LED was used. The emission wavelength is preferably 350 nm or more including the peak wavelength of the excitation spectrum of the JEM phase phosphor, and in particular, the emission peak wavelength of 390 nm to 420 nm is preferable with good electric / light conversion efficiency in the InGaN-based semiconductor light emitting device. However, here, an LED having an emission peak wavelength of 405 nm was used. Further, a semiconductor light emitting device having a p-type electrode and an n-type electrode on one surface was used.

Next, the light-emitting device 60 of Example 1 is demonstrated using FIG. 3 which is sectional drawing.
The light emitting device 60 includes a base 65, electrodes 66 and 67 formed on the surface of the base 65, a semiconductor light emitting element 64 electrically connected to the electrodes 66 and 67, and a silicone resin that seals the semiconductor light emitting element 64. 69, the blue phosphor 11, the blue-green phosphor 12 and the yellow phosphor 20 dispersed in the resin, and the range in which the silicone resin 69 is injected are limited, and the surface in contact with the silicone resin 69 is in a mirror shape Thus, the frame 68 is used for effectively extracting light. The electrodes 66 and 67 are three-dimensionally routed from the upper surface of the base 65 to the lower surface that is the mounting surface.

The blue phosphor 11 and the blue-green phosphor 12 are the above-described JEM phase phosphors. The blue phosphor 11 has an emission peak wavelength of about 478 nm, an emission spectrum full width at half maximum of about 115 nm, and the blue-green phosphor 12 emits light. The peak wavelength is about 505 nm, and the full width at half maximum of the emission spectrum is about 120 nm. The blue phosphor 11 and the blue-green phosphor 12 have a median particle size (D ₅₀ ) of 20 μm to 40 μm and a 90% particle size (D ₉₀ ) of 70 μm or less by a classification method such as sieve classification. The yellow phosphor 20 is the α sialon phosphor (compositional formula Ca _0.93 Eu _0.07 Si ₉ Al ₃ ON ₁₅ ) shown above, the emission peak wavelength is about 590 nm, and the full width at half maximum of the emission spectrum is about 90 nm. It is. Also for the yellow phosphor 20, the median particle size (D ₅₀ ) was set to 20 μm or more and 40 μm or less, and the 90% particle size (D ₉₀ ) was set to 70 μm or less by a classification method such as sieving classification. Silicone resin in which the mixing ratio (mass ratio) of the three types of phosphors is set to blue phosphor 11: blue-green phosphor 12: yellow phosphor 20 = 5: 5: 3 so that the emission color of the light-emitting device is white. 69.

  FIG. 4 shows an emission spectrum of a light emitting device in which the above three kinds of phosphors are mixed. As for the chromaticity of this light-emitting device, the white color of chromaticity x = 0.33 and chromaticity y = 0.36 was shown. The average color rendering index Ra, which is a measure of natural light emission, was as high as 89. The luminous intensity was 1800 millicandelas when the driving current of the semiconductor light emitting device 64 was 40 mA.

  In order to obtain a light emitting device having excellent color rendering properties, it is desirable that the full width at half maximum of each emission spectrum of the blue and blue-green phosphors is at least 80 nm. The emission spectrum of the JEM phase phosphor has a wide wavelength range of 100 nm or more, which is not often seen with other phosphors emitting in the blue region. Then, by using a mixture of two types of JEM phase phosphors having different emission peak wavelengths as in this example, the full width at half maximum of the synthesized emission spectrum is further widened. For this reason, it has been found that white light with excellent color rendering can be obtained by adding only one kind of yellow phosphor as a phosphor emitting a wavelength that cannot be covered by the JEM phase phosphor in the visible light region. Usually, when a mixture of various types of phosphors is used, there is a problem that the mixture becomes non-uniform due to the difference in material characteristics of the phosphor crystals. In this embodiment, the blue phosphor 11 and the blue-green color are mixed. The phosphor 12 has a slightly different composition ratio of La and Ce. Both have the same JEM phase crystal structure, and there is almost no difference in particle size distribution in the process of producing the phosphor powder. Also, the difference in atomic weight between La and Ce is slight (La = 139, Ce = 140), and the mass ratio in the rare earth (La, Ce) phosphor is small, so the difference in specific gravity is negligible. Therefore, there is almost no difference in the state of dispersion in the resin.

In addition, as a characteristic of the yellow phosphor, in order to obtain white light having excellent color rendering properties when used simultaneously with the blue phosphor 11 and the blue-green phosphor 12, the emission peak wavelength is particularly in the range of 565 nm to 605 nm, and the emission spectrum. A full width at half maximum of 80 nm or more is desirable. In consideration of the generation of white light in one light emitting device, it is necessary to have good luminous efficiency at the same excitation light source as the JEM phase phosphor used at the same time, that is, at an excitation wavelength of 350 nm to 420 nm. The yellow phosphor 20 (α sialon, composition formula Ca _0.93 Eu _0.07 Si ₉ Al ₃ ON ₁₅ ) used in this example has an emission peak wavelength of 590 nm and an emission spectrum full width at half maximum of about 90 nm or more. Has a wide range of features. Further, it has a strong excitation spectrum peak in the near ultraviolet region.

  Also, as the yellow phosphor, an oxynitride phosphor that is the same kind of material as the blue to blue-green phosphor and has a similar specific gravity is used, and the upper limit and the lower limit of the particle diameter of each phosphor are substantially the same. By sorting, the phosphor particles could be uniformly dispersed in the resin. Therefore, the influence of manufacturing variation was reduced, and when a plurality of light emitting devices of Example 1 were made and the luminescent color was examined, there was no variation in visual observation.

  Furthermore, since the composition of the yellow phosphor 20 and the JEM phase phosphor both include oxynitride phosphors, that is, silicon, aluminum, nitrogen and oxygen, and is common in that the ratio of silicon and nitrogen is large, It has a common characteristic that the temperature dependency of the luminous efficiency is small. Further, since the emission peak wavelength of the excitation light source is as short as 405 nm and there is almost no influence on the visibility, the emission color is almost determined only by the phosphor. Therefore, in this light emitting device, the change in chromaticity when the operating temperature is changed from 0 ° C. to 100 ° C. is 1/6 to 1 as compared with the light emitting device of Comparative Example 1 using the oxide phosphor described later. / 4 and has an excellent point that there is almost no change in color tone. In particular, in a light emitting device for illumination, since a large amount of heat is generated by passing a large current in order to increase luminance, the characteristic that the temperature change of chromaticity is small is important.

  In addition, since the used JEM phase phosphor and yellow phosphor 20 are physically and chemically stable oxynitride phosphors compared to phosphors such as sulfides, a long-life light-emitting device can be realized. .

(Comparative Example 1)
As an example of a light emitting device that has been used conventionally, there is a combination of a blue light emitting diode and a YAG: Ce ³⁺ phosphor that emits yellow fluorescence by excitation light emitted from the blue light emitting diode (Patent Document 1). The emission spectrum of the light emitting device of Comparative Example 1 having this configuration is shown in FIG. In this case, since the blue light emitted from the light emitting diode and the yellow light emitted from the YAG: Ce ³⁺ phosphor are in a complementary color relationship, the pseudo-white light is emitted, but the full width at half maximum of the emission spectrum of blue light is narrow. Therefore, there is a drop in emission intensity in the vicinity of 500 nm. For this reason, it becomes an unnatural emission spectrum different from natural light, and the average color rendering index Ra is 84, which is lower than that of this embodiment.

(Comparative Example 2)
As a comparative example of the prior art using three kinds of phosphors, the phosphor in Example 1 is BaMgAl ₁₀ O ₁₇ : Eu ²⁺ which is a blue phosphor, SrAl ₂ O ₄ : Eu ²⁺ which is a green phosphor, and red. A light emitting device in which the phosphor was replaced with 0.5 MgF ₂ .3.5MgO.GeO ₂ : Mn ⁴⁺ was produced. In this case, the emission spectrum as shown in FIG. 6 was obtained, and a neutral white color with chromaticity coordinates x = 0.35 and chromaticity coordinates y = 0.37 was obtained. Since the full width at half maximum of the emission spectrum of each phosphor was narrow, the emission spectrum obtained as a whole was also non-uniform, and the average color rendering index Ra was as low as 60. The luminous intensity of the light emitting device of Comparative Example 2 was 1120 millicandelas when the driving current of the semiconductor light emitting element 64 was 40 mA.

  In Example 1, it was shown that an emission spectrum close to natural light can be obtained by mixing JEM phase phosphors having different compositions. However, by finely adjusting the ratio of the JEM phase phosphor, the emission spectrum shape can be further improved. An example of improvement is shown in Example 2. The structure of the light emitting device is the same as that shown in FIG. 3, and the mixing ratio of the phosphors is changed.

  The blue component was increased by setting the mixing ratio of the blue phosphor 11, the blue-green phosphor 12, and the yellow phosphor 20 to 7: 5: 3.

  FIG. 7 shows an emission spectrum of the light emitting device in which the above three kinds of phosphors are mixed. As for the chromaticity of this light-emitting device, the white color of chromaticity x = 0.33 and chromaticity y = 0.35 was shown. The average color rendering index Ra, which is a measure of natural light emission, was as high as 90, and a more natural light emission spectrum than that of Example 1 was obtained.

  Next, Example 3 in which more natural light emission is realized by adding a red phosphor will be described. The structure of the light emitting device is obtained by changing the phosphor in the structure shown in FIG.

The blue phosphor 13 and the blue-green phosphor 14 have the composition formula z = 0.95 in the above-described JEM phase phosphor. The emission peak wavelength of the blue phosphor 11 is about 478 nm, the emission spectrum full width at half maximum is about 115 nm, the emission peak wavelength of the blue green phosphor 12 is about 505 nm, and the full width at half maximum of the emission spectrum is about 120 nm. The blue phosphor 13 and the blue-green phosphor 14 have a median particle size (D ₅₀ ) of 20 μm or more and 40 μm or less and a 90% particle size (D ₉₀ ) of 70 μm or less by a classification method such as sieving classification. The yellow phosphor 21 is the α sialon phosphor (composition formula (Ca _0.93 Eu _0.07 ) _0.25 Si _11.25 Al _0.75 ON _15.75 ) shown above, and the emission peak wavelength. Is about 580 nm, and the full width at half maximum of the emission spectrum is about 90 nm. The yellow phosphor 21 also had a median particle size (D ₅₀ ) of 20 μm or more and 40 μm or less and a 90% particle size (D ₉₀ ) of 70 μm or less by a classification method such as sieve classification. In order to obtain good color rendering properties, it is preferable that the emission peak wavelength of the yellow phosphor is 510 nm or more and 605 nm or less and the full width at half maximum of the emission spectrum is 80 nm or more.

Furthermore, in this example, the red phosphor 30 (CaAlSiN ₃ : Eu ³⁺ (Eu activation amount 0.8%)) described above was added in order to bring the emission spectrum closer to natural light. The red phosphor 30 has the characteristics that the emission peak wavelength is about 650 nm and the full width at half maximum of the emission spectrum is as wide as about 90 nm or more. The red phosphor 30 also had a median particle diameter (D ₅₀ ) of 20 μm or more and 40 μm or less and a 90% particle diameter (D ₉₀ ) of 70 μm or less by a classification method such as sieve classification. In order to obtain good color rendering, it is desirable that the emission peak wavelength of the red phosphor is 600 nm to 670 nm and the full width at half maximum of the emission spectrum is 80 nm or more.

  The phosphor mixture ratio (mass ratio) was set to blue phosphor 13: blue-green phosphor 14: yellow phosphor 21: red phosphor 30 = 8: 9: 4: so that the emission color of the light emitting device was white. 2 was dispersed in the silicone resin 69.

  An emission spectrum of a light emitting device in which the above four types of phosphors are mixed is shown in FIG. As for the chromaticity of this light-emitting device, the white color of chromaticity x = 0.36 and chromaticity y = 0.37 was shown. As can be seen from the emission spectrum, very flat emission was obtained over the entire wavelength range, and the average color rendering index Ra, which is a standard for natural emission, was as high as 97.

  Further, by using oxynitride phosphors or nitride phosphors of the same kind as the four types of phosphors and having a specific gravity close to each other, phosphor particles can be uniformly dispersed in the resin. Furthermore, since the phosphors are more uniformly mixed and dispersed by selecting so that the upper limit and the lower limit of the particle diameters of the phosphors are substantially the same, the influence of manufacturing variations is reduced.

  Further, since the red phosphor used in this example has a very high luminous efficiency, the emission intensity in the red region could be increased with a slight increase in the amount of addition.

(Other possible embodiments)
In each embodiment, the phosphor is dispersed in the silicone resin, but other resins such as an epoxy resin may be used, and the phosphor may be dispersed in a transparent material such as glass. As the green to red phosphor, materials other than those described in the embodiment or the comparative example, for example, a TAG (TbAl ₃ O ₁₂ ) phosphor may be used.

  Further, the mixing ratio of the phosphors described in each example is preferably adjusted as appropriate so that predetermined chromaticity can be obtained because the luminous efficiency of the phosphors varies depending on the production lot.

  In each embodiment, an LED is used as the semiconductor light emitting element, but a semiconductor laser may be used. The wavelength of the excitation light may be any wavelength as long as it has good electrical / optical conversion efficiency as a semiconductor light emitting device and is in the vicinity of the peak wavelength of the excitation spectrum of the phosphor.

  The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a measurement result of a typical excitation spectrum of the JEM phase phosphor described in the best mode of implementation. It is the measurement result of the typical emission spectrum of the JEM phase fluorescent substance demonstrated in the best form of implementation. 1 is a cross-sectional view of a light emitting device in Example 1. FIG. 2 is an emission spectrum of the light emitting device of Example 1. 2 is an emission spectrum of the light emitting device of Comparative Example 1. 6 is an emission spectrum of the light emitting device of Comparative Example 2. 3 is an emission spectrum of the light emitting device of Example 2. 6 is an emission spectrum of the light emitting device of Example 3.

Explanation of symbols

  11, 13 Blue phosphor, 12, 14 Blue green phosphor, 20, 21 Yellow phosphor, 30 Red phosphor, 40 Green phosphor, 60 Light emitting device, 65 Base, 66, 67 Electrode, 64 Semiconductor light emitting device, 68 Frame, 69 Silicone resin.

Claims (21)

A semiconductor light emitting element that emits excitation light; and
A light-emitting device comprising a plurality of phosphors that emit fluorescence by absorbing at least the excitation light,
The composition elements of the plurality of phosphors each include at least Si, Al, O, N, and Re (Re is one element of a lanthanoid rare earth common to the plurality of phosphors),
The light emitting device, wherein the emission peak wavelength in each of the plurality of phosphors is different due to a difference in the ratio of the composition element in each of the plurality of phosphors. The plurality of phosphors are:
The main crystal phase is the JEM phase,
Expressed by a composition formula _{M 1-x Ce x Al (} Si y1-z Al z) N y2-z O z,
M represents at least one element selected from the group consisting of La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu;
X is a real number satisfying 0.1 ≦ x ≦ 1,
Z is a real number satisfying 0.9 ≦ z ≦ 1.1;
The light-emitting device according to claim 1, wherein y1 is approximately 6 and y2 is approximately 10.   The light emitting device according to claim 2, wherein the plurality of phosphors have different values of x.   The light emitting device according to claim 3, wherein the plurality of phosphors include a phosphor having x of less than 0.5 and a phosphor having x of 0.5 or more.   5. The light emitting device according to claim 1, wherein the emission peak wavelengths of the plurality of phosphors are all 450 nm or more and 510 nm or less.   6. The light emitting device according to claim 1, wherein the full width at half maximum of the emission spectra of the plurality of phosphors is 80 nm or more.   The light emitting device according to any one of claims 1 to 6, wherein an upper limit and a lower limit of a particle diameter of the plurality of phosphors are substantially the same.   The light-emitting device according to claim 1, further comprising a phosphor that absorbs the excitation light and emits green to yellow light.   The light emitting device according to claim 8, wherein the phosphor emitting green to yellow light is an oxynitride phosphor.   The light emitting device according to claim 8 or 9, wherein the phosphor emitting green to yellow light is an Eu activated α sialon phosphor.   The light emitting device according to any one of claims 8 to 10, wherein an emission peak wavelength of the phosphor emitting green to yellow light is 510 nm or more and 605 nm or less.   The light emitting device according to any one of claims 8 to 11, wherein a full width at half maximum of an emission spectrum of the phosphor emitting green to yellow light is 80 nm or more.   The upper limit and the lower limit of the particle size of the phosphor emitting green to yellow light are substantially the same as the upper limit and the lower limit of the plurality of phosphors, respectively. Light-emitting device.   The light-emitting device according to claim 1, further comprising a phosphor that absorbs the excitation light and emits red light.   The light emitting device according to claim 14, wherein the phosphor emitting red light is an oxynitride phosphor or a nitride phosphor. The light-emitting device according to claim 14 or 15, wherein the phosphor that emits red light is Eu-activated CaSiAlN ₃ .   The light emitting device according to any one of claims 14 to 16, wherein an emission peak wavelength of the phosphor that emits red light is 600 nm or more and 670 nm or less.   18. The light emitting device according to claim 14, wherein a full width at half maximum of an emission spectrum of the phosphor emitting red light is 80 nm or more.   The upper limit and the lower limit of the particle size of the phosphor emitting red light are substantially the same as the upper and lower limits of the particle size of the plurality of phosphors, according to any one of claims 14 to 18. The light-emitting device of description.   20. The light-emitting device according to claim 1, wherein an emission peak wavelength of the excitation light is 350 nm or more and 420 nm or less.   The chromaticity coordinate x of light emission of the light emitting device is 0.22 to 0.44 and the chromaticity coordinate y is 0.22 to 0.44, or the chromaticity coordinate x of light emission from the light emitting device. The light emitting device according to claim 1, wherein the chromaticity coordinate y is 0.33 or more and 0.46 or less.

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