TWI628263B - Phosphor and illuminating device - Google Patents

Abstract

The present invention relates to a nitride phosphor which can realize high-luminance red light emission, and a light-emitting device which is excellent in color rendering properties and luminous efficiency by using the phosphor.

The phosphor of the present invention is characterized by the formula: M1 _a M2 _b M3 _c M4 _d N _e O _f , M1 is an element selected from the group consisting of Eu and Ce, and M2 is selected from Mg. And one or more elements of Ca, Sr, Ba, and Zn, M3 is an element selected from the group consisting of Al, Ga, In, and Sc, and M4 is selected from Si, Ge, Sn, and Ti, which is necessary for Si. One or more elements of Zr and Hf, N is nitrogen, O is oxygen, a~f is 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦d≦1.5, c+d= 2. 2.5≦e≦3.0, 0≦f≦0.5, and a flat plate having an average particle diameter of 1 μm or more and 30 μm or less and a thickness of 1/3 or less of the average particle diameter.

Description

Phosphor and illuminating device

The present invention relates to a phosphor for an LED (Light Emitting Diode) or an LD (Laser Diode), and a light-emitting device using the same. More specifically, it relates to a nitride phosphor that can realize high-luminance red light emission, and a light-emitting device that is excellent in color rendering properties and luminous efficiency by using the phosphor.

In the case of white LEDs for illumination, a combination of a blue LED chip and a yellow phosphor to obtain approximate white light is widely spread. However, in the white LED of this mode, although the chromaticity coordinate value falls into the white area, since the luminescent component of the red area or the like is small, the vision of the object illuminated by the white LED is greatly different from the vision of the object illuminated by the natural light. . That is, the white LED does not perform well in the color rendering of the indicator of the visual naturalness of the object.

Then, by combining a red phosphor or an orange phosphor in addition to the yellow fluorescent light to compensate for the insufficient red component, the color-developed white LED is put to practical use. For example, Patent Document 1 discloses a light-emitting device in which a yellow-colored YAG phosphor and a red-emitting nitride and an oxynitride phosphor are used in order to compensate for a red component of a white LED.

However, since it is inevitable that the luminous efficiency tends to decrease when the color rendering property is to be improved, it is necessary to use a red phosphor having a higher brightness in order to achieve a balance between color rendering properties and luminous efficiency. Regarding such a high-intensity red phosphor, Patent Document 2 discloses an Eu ²⁺ -activated CaAlSiN ₃ . Further, this document discloses that a phosphor having a light-emitting peak wavelength shifted to the short-wavelength side can be obtained by substituting a part of Ca with Sr. Since the emission wavelength of the Eu ²⁺ -activated (Sr, Ca) AlSiN ₃ -based nitride fluorescent system is shorter than that of the CaAlSiN ₃ -based nitride phosphor, the spectral component of the region with high visual sensitivity increases, so it is effective as high. Bright red phosphor for white LEDs.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-071726

[Patent Document 2] International Gazette No. 2005/052087

On the other hand, when the luminous efficiency of the phosphor is observed from the viewpoint of the particle size distribution, the quantum efficiency of the phosphor tends to increase as the particle size of the phosphor increases, so that a higher luminance is used to use the particle diameter. Larger phosphors are preferred. However, if the particle size of the phosphor is too large, problems such as sedimentation and separation of the phosphor particles or clogging of the dispenser nozzle may occur in the paste obtained by mixing the phosphor and the sealing resin.

Therefore, in a white LED in which a semiconductor light-emitting element and a phosphor are combined to emit white light, a red phosphor which can emit light of higher brightness can be realized without impeding operability.

In order to solve the above problems, the present inventors have found that the shape of the phosphor particles is controlled to have a flat shape (sheet shape) having a specific average particle diameter and thickness by focusing on the particle shape of the phosphor. The phosphor particles are aligned to each other to form a dense phosphor powder layer, and as a result, high-luminance red light emission can be realized, and the present invention can be completed.

That is, the gist of the present invention is a phosphor represented by the general formula: M1 _a M2 _b M3 _c M4 _d N _e O _f , and M1 is an element selected from the group consisting of Eu and Ce, and M2 is One or more elements selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, M3 is an element selected from the group consisting of Al, Ga, In, and Sc, and M4 is selected from Si, Ge, and Sn, which are necessary for Si. One or more elements of Ti, Zr and Hf, N is nitrogen, O is oxygen, a~f is 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦d≦1.5, c +d=2, 2.5≦e≦3.0, 0≦f≦0.5, and the average particle diameter is 1 μm or more and 30 μm or less, and the thickness is a plate shape of 1/3 or less of the average particle diameter.

The fluorescent system of the present invention has a platelet shape having an average particle diameter of 1 μm or more and 30 μm or less and a thickness of 1/3 or less of the average particle diameter, and has a peak having a peak in a wavelength range of 250 nm or more and 550 nm or less, in particular, blue light excitation at 455 nm. In the case of a red light-emitting phosphor having a peak wavelength (λp) of an emission spectrum of 600 nm or more and 635 nm or less. Since the phosphor particles are in the form of a flat plate, when the phosphor is attached to the light-emitting device, the particles can be aligned so as to overlap each other to form a dense phosphor powder layer, and high-luminance red light emission can be realized.

Further, in the light-emitting device of the present invention, by using the phosphor, high-intensity white light excellent in balance between color rendering properties and luminous efficiency can be emitted.

Fig. 1 is an SEM image of the phosphor of Example 1.

Fig. 2 is an SEM image of the phosphor of Comparative Example 1.

3 is a flow chart showing a method of manufacturing the phosphor of Example 1.

[Formation of the Invention]

The fluorescent system of the present invention is represented by the formula: M1 _a M2 _b M3 _c M4 _d N _e O _f . This general formula shows the composition formula of the phosphor, and a to f are atomic ratios of the respective elements in the case where a + b = 1 is calculated.

M1 is an activator added to the parent crystal, that is, an element constituting the luminescent center ion of the phosphor, and is either or both of Eu or Ce. M1 can be selected according to the desired wavelength of light emission, preferably Eu.

When the amount of addition of M1 is too small, sufficient luminescence peak intensity cannot be obtained. When the amount is too large, the concentration extinction becomes large and the luminescence peak intensity tends to be low. As a result, a high-luminance phosphor cannot be obtained. Therefore, the addition amount a of M1 is 0.00001 or more and 0.15 or less.

M2 is one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and is preferably either one of Ca and Sr or both.

The total content b of M2 and the content a of M1 are 1, that is, the value of a+b=1 is satisfied.

M3 is one or more elements selected from the group consisting of Al, Ga, In, and Sc , Al is preferred. If the content of M3 is too small, the target phosphor crystals may not be obtained, and if too large, a heterogeneous phase may occur, and the yield tends to decrease. Therefore, the content c of M3 is 0.5 or more and 1.5 or less.

M4 is an element selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf, and Si is preferable, and Si monomer is preferable. If the content of M4 is too small, the target phosphor crystals may not be obtained, and if too large, a heterogeneous phase may occur, and the yield tends to decrease. Therefore, the content d of M4 is 0.5 or more and 1.5 or less. Further, the total content c of M3 and the content d of M4 are 2, that is, c + d = 2.

In the above formula, N is nitrogen and O is oxygen. The content e of N is 2.5 or more and 3.0 or less, preferably 2.7 or more and 3.0 or less. Further, the content f of O is 0 or more and 0.5 or less, preferably 0.3 or less.

The particle shape of the phosphor of the present invention is a flat plate shape. The shape of the tabular particles includes a circular plate, an elliptical shape, a polygonal shape, a shape in which a part or all of the polygonal shape is lacking, and the like. When the phosphor is attached to the light-emitting device, for example, when the phosphor is dispersed in the resin adhesive and applied to the reflective cup of the light-emitting device, the particles can be formed to overlap each other to form a dense firefly. The light powder layer is used to achieve high brightness. The particle shape can be confirmed by observation using a stereoscopic microscope or a scanning electron microscope (hereinafter referred to as SEM).

When the average particle diameter of the phosphor is too small, the absorption efficiency of the excitation light is poor, and sufficient light-emitting efficiency cannot be obtained. If the phosphor is too large, it is not suitable for mounting the light-emitting element, and therefore the average particle diameter is 1 μm or more and 30 μm or less. In the case of an elliptical or polygonal shape, the long axis and the short axis can be flattened Both are considered as average particle sizes.

The thickness of the phosphor is 1/3 or less of the average particle diameter, preferably 1/4 or less, more preferably 1/5 or less. The lower limit of the thickness is not particularly limited, but is preferably 1/20 or more of the average particle diameter, more preferably 1/15 or more, still more preferably 1/10 or more. When the ratio of the thickness/average particle diameter of the phosphor is too large, a dense phosphor powder layer cannot be formed, and if it is too small, manufacturing or handling is difficult.

The fluorescent system of the present invention is preferably produced by a mixing process using a mixed raw material, a baking process of a raw material after a baking mixing process, and a pulverizing process of a sintered body after a pulverization baking process. In addition, it is better to use an additional acid treatment process and an annealing process. With respect to the produced phosphor, the impurities remaining on the surface can be vaporized and removed by an acid treatment process, and the surface layer of the phosphor can be made more dense by annealing.

A flux can also be used in the roasting process. By using a flux to promote grain growth, the brightness of the phosphor is increased. Flux can also be used in combination. In this case, the effect of the flux can be continued by using two or more kinds of fluxes having a large difference in melting point.

In terms of flux, there are ammonium halides such as NH ₄ Cl; alkali metal carbonates such as Na ₂ CO ₃ and Li ₂ CO ₃ ; and alkali metal halides such as LiCl, NaCl, KCl, RbCl, LiF, NaF, KF, and RbF. Alkaline earth metal carbonates such as CaCO ₃ , SrCO ₃ , BaCO _{3 ,} etc.; alkaline earth metal oxides such as MgO, CaO, SrO, BaO, etc.; MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl ₂ , MgF ₂ , CaF ₂ , alkaline earth metal halides such as SrF ₂ and BaF ₂ ; boron oxides such as B ₂ O ₃ ; phosphate compounds such as Li ₃ PO ₄ , Na ₃ PO ₄ , NH ₄ H ₂ PO _{4 ,} etc.; AlF ₃ , ZnCl _{2, ZnF 2, NbCl 5,} NbF 5, MoCl 5, TaCl 5, WCl 5, ReCl 5, OsCl 3, IrCl 3 , etc. _{halide; Nb 2 O 3, MoO 3} , Ta 2 O 5, WO 3, Re Oxide of ₂ O ₇ , OsO ₄ , IrO _{2 ,} etc.; nitride of BN, Li ₃ N, Ca ₃ N ₂ , Sr ₃ N ₂ , Ba ₃ N _{2 ,} etc.; LaF ₃ , GdF ₃ , LuF ₃ , YF _{3 , ScF 3, LaCl 3, GdCL} 3, LuCl 3, YCl 3, ScCl 3 , etc. rare-earth element _{halides; La 2 O 3, Gd 2} O 3, Lu 2 O 3, Y 2 O 3, Sc 2 O 3 Etc. Rare earth element oxides.

The particle shape, the average particle diameter, and the thickness of the phosphor can be adjusted depending on the composition ratio of the elements constituting the phosphor, the baking temperature, the use of the flux, and the like.

For example, when M2 is composed of Ca and Sr, the ratio of the number of atoms of Sr to the total number of atoms of Ca and Sr (Sr/(Sr+Ca)) is preferably 0.83 or more and 0.95 or less, and 0.85 or more and 0.95 or less. Better.

Further, when M3 is Al and M4 is Si, the Mo ratio (Si/Al) of Si to Al is preferably 0.82 or more and 1.00 or less, and more preferably 0.85 or more and 1.00 or less.

The calcination temperature is generally applicable to the temperature of the nitride phosphor, for example, 1200 ° C or more and 2000 ° C or less, more preferably 1500 ° C or more and 1850 ° C or less, and typically can be set to 1800 ° C or so, but it can be used in accordance with The raw material powder to be used, the desired particle size and the like are suitably adjusted.

As described above, since the average particle diameter of the fluorescent system of the present invention is 1 μm or more and 30 μm or less and the thickness is 1/3 or less of the average particle diameter, the particles can be aligned to form a dense one. A phosphor powder layer. Therefore, high-intensity red light emission can be achieved.

The light-emitting device of the present invention has the above-described phosphor and light-emitting element of the present invention.

For the light-emitting element, an ultraviolet LED, a blue LED, or a phosphor can be used. A single element of the lamp or a combination of these. The light-emitting element is preferably light having a wavelength of 250 nm or more and 550 nm or less, and more preferably a blue LED light-emitting element of 420 nm or more and 500 nm or less.

In the phosphor used in the light-emitting device, in addition to the phosphor of the present invention, a phosphor having other luminescent colors may be used in combination. Examples of the other luminescent color phosphor include a blue luminescent phosphor, a green luminescent phosphor, a yellow luminescent phosphor, and an orange luminescent phosphor, and examples thereof include Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce. CaSc ₂ O ₄ :Ce, Y ₃ Al ₅ O ₁₂ :Ce, Tb ₃ Al ₅ O ₁₂ :Ce, (Sr, Ca, Ba) ₂ SiO ₄ :Eu, La ₃ Si ₆ N ₁₁ :Ce, Sr ₂ Si ₅ N ₈ : Eu et al. The phosphor which can be used in combination with the phosphor of the present invention is not particularly limited, and can be appropriately selected in accordance with the brightness and color rendering properties required for the light-emitting device. By mixing the phosphor of the present invention with other phosphors of luminescent color, it is possible to realize white of various color temperatures of daylight white to bulb color.

In terms of a light-emitting device, there are a lighting device, a backlight device, an image display device, and a signal device.

In the light-emitting device of the present invention, by using the phosphor of the present invention, the balance between luminous efficiency and color rendering property is excellent, and white light of high luminance can be realized.

[Examples]

Hereinafter, the present invention will be described in more detail by way of the following examples. Table 1 shows the composition ratio, particle shape, average particle diameter, thickness, and relative luminescence peak intensity (%) of the phosphors of the examples and the comparative examples.

[Example 1]

As shown in Fig. 3, the fluorescent material of Example 1 was produced by a mixing process of a mixed raw material, a baking process of a raw material after a baking mixing process, a crushing process of a sintered body after a pulverization baking process, an acid treatment process, and an annealing process. body.

<mixed engineering>

In order to be α-type tantalum nitride powder (NP-400 grade, 1.0% by mass of Oxygen Chemical Industry Co., Ltd., oxygen content: 1.0% by mass), aluminum nitride powder (F grade of Tokuyama Co., Ltd., oxygen content: 0.6% by mass) 23.25% by mass and a cerium oxide powder (RU grade manufactured by Shin-Etsu Chemical Co., Ltd.) were weighed in a manner of 0.80% by mass, and the raw material powder was dry-mixed in a V-type mixer for 10 minutes. In order to make the size of the raw materials uniform, the mixed raw materials were passed through a nylon sieve of 250 μm mesh for use in the following works.

In a glove box of a nitrogen atmosphere having a water content of 1 ppm or less and an oxygen content of 1 ppm or less, it is made into a calcium nitride powder (manufactured by High Purity Chemical Research Co., Ltd.: purity 2N) of 2.58 mass% and tantalum nitride powder (high purity chemical research). The company made a weighing of 2N) 49.50% by mass, and dry-mixed with the above-mentioned raw materials that have passed through the sieve. The mesh was again sieved with a mesh of 250 μm mesh, and 300 g of the passed sieve was filled in a cylindrical boron nitride container (N-1 grade, manufactured by Electric Chemical Industry Co., Ltd.) with a lid.

<Roasting Engineering>

The raw materials are set together with the container in an electric furnace to be roasted. The baking is performed in an electric furnace using a carbon heater. After degassing to a vacuum, the temperature is raised at a rate of 5 ° C / min. From 500 ° C, a gas is introduced at a flow rate of 5 liters / min of nitrogen gas at 0.9 MPa. In a pressurized nitrogen atmosphere of G, heat treatment was carried out at 1800 ° C for 4 hours. After the end of the roasting, the container was taken out and placed until room temperature. The obtained calcination system is gradually agglomerated in a block shape.

<Crushing Engineering>

The bulk sintered body was pulverized by a roller mill. It was only classified into a sieve which passed through a mesh of 150 μm among the pulverized synthetic powder.

<acid treatment engineering>

The sieved synthetic powder was poured into 2.0 M hydrochloric acid so that the slurry concentration became 25% by mass, and the acid treatment was performed by immersion for 1 hour. After the acid treatment, the slurry was stirred for 1 hour while stirring the hydrochloric acid slurry.

The boiled synthetic powder was cooled to room temperature and filtered, and the acid treatment liquid was separated from the synthetic powder. The synthetic powder after separating the acid treatment liquid is placed in a dryer having a temperature of 100 ° C to 120 ° C. In the hour, only the sieve which passed through the mesh of 150 μm was classified into the dried synthetic powder.

<annealing engineering>

The synthetic powder obtained by the acid treatment process was filled in a crucible made of alumina, heated in the air at a temperature elevation rate of 10 ° C /min, and heat-treated at 400 ° C for 3 hours. After the heat treatment, the film was allowed to stand at room temperature, and the phosphor of Example 1 was obtained.

The fluorescent system of Example 1 is represented by the general formula: M1 _a M2 _b M3 _c M4 _d N _e O _f , M1 is Eu, M2 is Sr and Ca, M3 is Al, M4 is Si, N is nitrogen, and O is Oxygen, the content of each element a~f, the occupation ratio of Sr (Sr/(Sr+Ca)), and the Si/Al ratio are the values shown in Table 1. Specifically, it is a phosphor represented by Eu _0.008 (Sr, Ca) _0.992 Al _1.05 Si _0.95 N _3.0 , wherein a~f satisfies 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦d≦1.5, c+d=2, 2.5≦e≦3.0, 0≦f≦0.5, and Sr/(Sr+Ca)=0.90, Si/Al=0.90.

The fluorescent system particles of Example 1 had a flat plate shape, and had an average particle diameter of 16.0 μm, a thickness of 2.5 μm, and a thickness/average particle diameter of 0.2. The image obtained by the SEM of the phosphor of Example 1 is shown in Fig. 1.

The particle shape was confirmed by SEM observation by randomly extracting 10 manufactured phosphors.

The thickness is the arithmetic mean of the 10 phosphor particles extracted as described above. The thickness of each of the phosphor particles is the thickness of the central portion in the longitudinal direction of the plate-shaped phosphor particles.

The average particle size is based on laser diffraction using a particle size distribution measuring device. Particle diameter distribution measurement by scattering method, integral calculation on volume basis The value of the 50% diameter (D50) in the rate.

Thickness/average particle size is the value obtained by rounding off the second decimal place.

The luminescent properties of the phosphor of Example 1 were evaluated as follows.

The phosphor of Example 1 was filled in a concave member to smooth the surface to mount the integrating sphere. Monochrome light that is split from a illuminating light source (Xe lamp) into a predetermined wavelength is introduced into the integrating sphere using an optical fiber. The monochromatic light was used as an excitation source to irradiate the sample, and a spectrophotometer (QE-1100 manufactured by Otsuka Electronics Co., Ltd.) was used to measure the fluorescence of the phosphor sample and the reflected light. In terms of monochromatic light, blue light having a wavelength of 455 nm is used.

The relative luminescence peak intensity is calculated from the product of the fluorescence spectrum and the standard luminosity. The other examples and comparative examples described below were also measured under the same conditions as in Example 1, and Example 1 was shown as a relative value of 100%. The relative luminescence peak intensity was set to 90% or more as a pass.

[Examples 2 to 5]

As shown in Table 1, in the fluorescent systems of Examples 2 to 5, the values of a to f of the composition formula of the phosphor of Example 1, Sr/(Sr+Ca), and Si/Al were changed to change the average particle size. Diameter and thickness. The shape of the particles is flat.

The phosphors of Examples 2 to 5 were all phosphors having a relative luminescence peak intensity of 90% or more. In the phosphor of Example 3, although the value of the thickness/average particle diameter was increased to 0.3, the relative luminescence peak intensity was 95%. In the fluorescent system of Example 4, oxygen was added based on the composition formula of the phosphor of Example 3, and Sr/(Sr+Ca) was a low value of 0.83, but the relative luminescence peak intensity was 94%. . The fluorescent system of Example 5 was irradiated with the fluorescence of Example 1. Based on the composition of the body, oxygen is added. Although Si/Al is a lower value of 0.82, the relative luminescence peak intensity is 92%.

[Comparative Examples 1 to 3]

In the phosphor of Comparative Example 1, Sr/(Sr+Ca) was set to 0.80 and Si/Al was set to 1.15, and the baking temperature was changed as compared with the phosphor of Example 1. Since the particle shape of the obtained phosphor is columnar, the thickness of the particle cannot be measured. The relative luminescence peak intensity of the phosphor of Comparative Example 1 was 88%, which did not reach the acceptable value. The SEM image of the phosphor of Comparative Example 1 is shown in Fig. 2 .

In the phosphor of Comparative Example 2, Sr/(Sr+Ca) was set to 0.80, Si/Al was set to 0.80, and the baking temperature was changed as compared with the phosphor of Example 1. Since the particle shape of the obtained phosphor is spherical or columnar, the thickness of the particles cannot be measured. The relative luminescence peak intensity of the phosphor of Comparative Example 2 was 79%, which did not reach the acceptable value.

The phosphor of Comparative Example 3 was increased in the ratio of Eu and the Sr ratio in M2 as compared with the phosphor of Example 1. Since the particle shape of the obtained phosphor is spherical, the thickness of the particles cannot be measured. The relative luminescence peak intensity of the phosphor of Comparative Example 3 was 88%, which did not reach the acceptable value.

Further, although not shown in Table 1, a phosphor obtained by substituting Ce for the phosphor of the phosphor of Example 1 is produced; and M2 is formed by using any of Mg, Ba, and Zn other than Ca or Sr. The phosphor is M3, which is a phosphor obtained by using any of Ga, In, and Sc other than Al; and M4 is one element selected from the group consisting of Ge, Sn, Ti, Zr, and Hf in addition to Si. The phosphors are all formed into a flat plate having an average particle diameter of 1 μm or more and 30 μm or less and a thickness of 1/3 or less of the average particle diameter, and the same evaluation as described above is performed. It was confirmed that the relative luminescence peak intensity was 90% or more.

[Embodiment 6]

A general cannonball type was produced by using a phosphor including the phosphor of the first embodiment, a phosphor for green emission, a phosphor of a blue-emitting phosphor, and a blue light-emitting LED chip as a light-emitting element. White light device. This light-emitting device has high luminance compared with the light-emitting device in which the phosphor of Comparative Example 1 is used instead of the phosphor of Example 1.

By using this light-emitting device, a high-brightness backlight device, an image display device, and a signal device can be realized.

Claims (3)

A phosphor represented by the formula: M1 _a M2 _b M3 _c M4 _d N _e O _f , M1 is Eu, M2 is Ca and Sr, M3 is Al, M4 is Si, N is nitrogen, and O is oxygen. , a~f is 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦d≦1.5, c+d=2, 2.5≦e≦3.0, 0≦f≦0.5, main crystalline phase It is a (Sr, Ca)AlSiN ₃ crystal phase, and the average particle diameter is 1 μm or more and 30 μm or less, and the thickness is 1/3 or less of the average particle diameter, and the ratio of the number of atoms of Sr in the M2 element (Sr/( Sr+Ca)) is 0.83 or more and 0.95 or less. The phosphor of claim 1, wherein the molar ratio of Si to Al (Si/Al) is 0.82 or more and 1.00 or less. A light-emitting device comprising the phosphor of claim 1 or 2 and a light-emitting element.