阅读说明：本技术 荧光体粉末、复合体和发光装置 (Phosphor powder, composite, and light-emitting device ) 是由 武田雄介 野见山智宏 高村麻里奈 奥园达也 宫崎胜 渡边真太郎 于 2020-03-24 设计创作，主要内容包括：本发明的一个方案是一种由含有Eu的α型塞隆荧光体粒子构成的荧光体粉末。该荧光体粉末的利用激光衍射散射法测定的体积基准的中值粒径(D-(50))为10μm～20μm,对波长600nm的光的扩散反射率为93％～99％。(One embodiment of the present invention is a phosphor powder composed of α -type sialon phosphor particles containing Eu. The phosphor powder has a volume-based median particle diameter (D) measured by a laser diffraction scattering method 50 ) 10-20 μm, and a diffuse reflectance of 93-99% for light with a wavelength of 600 nm.)

1. A phosphor powder comprising Eu-containing alpha-sialon phosphor particles,

by usingVolume-based median diameter D measured by laser diffraction scattering method₅₀Is 10-20 μm in diameter,

the diffuse reflectance for light with the wavelength of 600nm is 93-99%.

2. The phosphor powder according to claim 1, wherein the diffuse reflectance for light having a wavelength of 600nm is 94% to 99%.

3. The phosphor powder according to claim 1 or 2, wherein the diffuse reflectance for light having a wavelength of 500nm is 66% to 80%.

4. The phosphor powder according to any one of claims 1 to 3, wherein X1-X2, which is a difference between a diffuse reflectance X1 for light having a wavelength of 800nm and a diffuse reflectance X2 for light having a wavelength of 600nm, is 3.0% or less, and the unit of the diffuse reflectance X1 and the diffuse reflectance X2 is%.

5. The phosphor powder according to any one of claims 1 to 4, wherein D represents a volume-based cumulative 10% particle diameter and a volume-based cumulative 90% particle diameter measured by a laser diffraction scattering method₁₀、D₉₀When (D)₉₀－D₁₀)/D₅₀1.0 to 1.5.

6. The phosphor powder according to any one of claims 1 to 5, wherein the α -type sialon phosphor particles are composed of an α -type sialon phosphor containing Eu element, the α -type sialon phosphor being represented by a general formula: (M1_x，M2_y，Eu_z)(Si_12－(m+n)Al_m+n)(O_nN_16－n) In the general formula, M1 is a 1-valent Li element, M2 is a 2-valent Ca element, x is more than or equal to 0 and less than 2.0, y is more than or equal to 0 and less than 2.0, z is more than 0 and less than or equal to 0.5, x + y is more than 0 and less than or equal to 0.3 and less than or equal to x + y + z and less than or equal to 2.0, M is more than 0 and less than or equal to 4.0, and n is more than 0 and less than or equal to 3.0.

7. The phosphor powder of claim 6, wherein 1.5 < x + y + z ≦ 2.0.

8. The phosphor powder according to claim 6 or 7, wherein 0. ltoreq. x.ltoreq.0.1.

9. The phosphor powder according to any one of claims 1 to 8, wherein an emission peak wavelength is 590nm or more.

10. A composite comprising the phosphor powder according to any one of claims 1 to 9 and a sealing material for sealing the phosphor powder.

11. A light-emitting device is provided with:

a light emitting element that emits excitation light; and

the complex of claim 10 that converts the wavelength of the excitation light.

Technical Field

The invention relates to a phosphor powder, a composite, and a light-emitting device.

Background

As nitride and oxynitride phosphors, α -type sialon phosphors obtained by activating a specific rare earth element are known to have useful fluorescence characteristics, and are used in white LEDs and the like. In the α -sialon phosphor, the Si — N bond portion of the α -type silicon nitride crystal is substituted with Al — N bond and Al — O bond, and in order to maintain electrical neutrality, there is a structure in which specific elements (Ca, Li, Mg, and Y, or lanthanoid metal excluding La and Ce) intrude into and are solid-dissolved in the crystal lattice between the crystal lattices. The fluorescent property is exhibited by using a rare earth element as a luminescence center as a part of the element which enters into the solid solution. Among them, an α -sialon phosphor obtained by dissolving Ca in a solid solution and substituting Eu for a part thereof is excited relatively efficiently in a wide wavelength region from the ultraviolet region to the cyan region, and exhibits yellow to orange emission. As an attempt to further improve the fluorescence characteristics of such an α -sialon phosphor, for example, it has been proposed to select an α -sialon phosphor having a specific average particle diameter by classification (patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-96882

Disclosure of Invention

In recent years, further enhancement of luminance of white LEDs is required. For example, further improvement in light emission characteristics of phosphor powder used for white LEDs is also required.

The present invention has been made in view of the above problems. The present invention aims to provide a phosphor powder having improved light emission characteristics.

According to the present invention, there is provided a phosphor powder comprising Eu-containing α -sialon phosphor particles measured by a laser diffraction/scattering methodVolume-based median particle diameter (D)₅₀) 10-20 μm, and a diffuse reflectance of 93-99% for light with a wavelength of 600 nm.

Further, according to the present invention, there is provided a composite comprising the above phosphor powder and a sealing material for sealing the phosphor powder.

Further, according to the present invention, there is provided a light-emitting device including a light-emitting element that emits excitation light and the complex that converts the wavelength of the excitation light.

Effects of the invention

According to the present invention, a technique relating to a phosphor powder having improved light emission characteristics can be provided.

Drawings

FIG. 1 shows the median particle diameter (D) of a conventional phosphor powder₅₀) Relationship with the diffuse reflectance with respect to light having a wavelength of 600nm, and the median diameter (D) defined for the phosphor powder of the present embodiment₅₀) And a conceptual view of the range of diffuse reflectance for light having a wavelength of 600 nm.

Fig. 2 is a schematic cross-sectional view showing a structure of a light-emitting device according to an embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

The phosphor powder of the embodiment is a phosphor powder composed of α -type sialon phosphor particles containing Eu. The phosphor powder has a volume-based median particle diameter (D) measured by a laser diffraction scattering method₅₀) 10-20 μm, and a diffuse reflectance of 93-99% for light with a wavelength of 600 nm.

According to the phosphor powder of the present embodiment, the fluorescence characteristics of conventional α -sialon phosphor particles can be improved while maintaining the excitation wavelength region and the fluorescence wavelength region. Therefore, as a result, the light-emitting characteristics of the light-emitting device obtained by using the phosphor powder of the present embodiment can be improved.

Although the detailed mechanism is not clear for this reason, it is considered that the fluorescence characteristics of the phosphor powder are improved by making the median particle diameter in the range of 10 μm to 20 μm and the diffuse reflectance with respect to light having a wavelength of 600nm in the range of 93% to 99% at the same time.

(alpha-sialon phosphor particle)

The α -type sialon phosphor particles containing Eu are composed of an α -type sialon phosphor described below.

The alpha-sialon phosphor is represented by the general formula: (M1_x，M2_y，Eu_z)(Si_12－(m+n)Al_m+n)(O_nN_16－n) (wherein M1 is a 1-valent Li element, and M2 is 1 or more 2-valent elements selected from Mg, Ca and lanthanides (excluding La and Ce)).

The solid solution composition of the alpha-sialon phosphor is represented by x, y, z in the above general formula and m and N determined by the Si/Al ratio and O/N ratio accompanying them, and is 0. ltoreq. x < 2.0, 0. ltoreq. y < 2.0, 0. ltoreq. z < 0.5, 0. ltoreq. x + y, 0.3. ltoreq. x + y + z < 2.0, 0. ltoreq. m.ltoreq.4.0, and 0. ltoreq. n.ltoreq.3.0. In particular, when Ca is used as M2, the α -sialon phosphor is stabilized in a wide composition range, and a part thereof is replaced with Eu, which is a light emission center, and excited by light in a wide wavelength range from ultraviolet to cyan, whereby a phosphor exhibiting visible light emission from yellow to orange can be obtained.

In addition, from the viewpoint of obtaining bulb color light in illumination applications, the α -sialon phosphor preferably does not contain Li as a solid solution composition or contains a small amount of Li. In the above general formula, it is preferable that 0. ltoreq. x.ltoreq.0.1. And/or the ratio of Li in the α -sialon phosphor is preferably 0 to 1 mass%.

In general, an α -type sialon phosphor cannot be strictly defined in a solid solution composition by composition analysis or the like because of a second crystal phase different from the α -type sialon phosphor and an amorphous phase inevitably present. The α -sialon phosphor is preferably an α -sialon single phase as a crystal phase, and aluminum nitride or a polytype thereof may be contained as another crystal phase.

In the α -type sialon phosphor particles, a plurality of equiaxed primary particles are sintered to form massive secondary particles. The primary particles in the present embodiment are the smallest particles that can exist alone and can be observed by an electron microscope or the like. The shape of the α -sialon phosphor particle is not particularly limited. Examples of the shape include a spherical body, a cubic body, a columnar body, and an irregular shape.

The median particle diameter (D) of the phosphor powder of the present embodiment₅₀) Is 10 μm or more, more preferably 12 μm or more. The phosphor powder of the present embodiment has a median particle diameter (D)₅₀) The upper limit of (B) is 20 μm or less, more preferably 18 μm or less. The median particle diameter (D) of the phosphor powder of the present embodiment₅₀) The size of the secondary particles is described above.

Here, the median diameter (D) of the phosphor powder₅₀) Means according to JIS R1629: 199, 50% particle diameter in volume-based cumulative fraction measured by laser diffraction scattering method.

The phosphor particles of the present embodiment satisfy the requirement of reducing the median diameter (D)₅₀) The above range and the diffuse reflectance for light having a wavelength of 600nm are set to 93% to 99%. Diffuse reflectance can be measured by an ultraviolet-visible spectrophotometer equipped with an integrating sphere device. From the viewpoint of further improving the light emission characteristics, the diffuse reflectance for light having a wavelength of 600nm is preferably 94% to 99%, and more preferably 94% to 96%.

FIG. 1 shows the median particle diameter (D) of a conventional phosphor powder₅₀) Relationship with the diffuse reflectance with respect to light having a wavelength of 600nm and the median diameter (D) defined for the phosphor powder of the present embodiment₅₀) And a conceptual view of the range of diffuse reflectance for light having a wavelength of 600 nm.

Based on the findings on the α -sialon phosphor accumulated so far, it is considered that the conventional α -sialon phosphor powder has a diffuse reflectance for light having a wavelength of 600nm and a median particle diameter (D)₅₀) Is plotted in fig. 1, is located in the vicinity of the curve shown in fig. 1. In contrast, it was found that the phosphor powder of the present embodiment has a median particle diameter (D) obtained by optimizing the production method described later₅₀) The light emission characteristics can be improved by adjusting the diffusion reflectance to a value higher than that of the conventional range of 93 to 99% in the range of 10 to 20 μm.

The phosphor powder of the present embodiment has a median particle diameter (D)₅₀) And the diffuse reflectance are set to the above-described predetermined ranges, respectively, and at least one of the following conditions is satisfied, whereby the light emission characteristics can be further improved.

(i) D represents a volume-based cumulative 10% particle diameter and a volume-based cumulative 90% particle diameter measured by a laser diffraction scattering method₁₀、D₉₀When (D)₉₀－D₁₀)/D₅₀Is 1.0 to 1.5

(ii) The diffusion reflectivity of the light with the wavelength of 500nm is 66 to 80 percent

(iii) The difference (X1-X2) between the diffuse reflectance X1 (%) for light with a wavelength of 800nm and the diffuse reflectance X2 (%) for light with a wavelength of 600nm is 3.0 (%) or less

The phosphor powder described above is compatible with a volume-based median particle diameter (D) measured by a laser diffraction scattering method₅₀) The fluorescence characteristics can be improved by setting the range of 10 to 20 μm and the range of 93 to 99% in diffuse reflectance for light having a wavelength of 600 nm.

(method for producing phosphor powder)

A method for producing a phosphor powder composed of α -sialon phosphor particles according to this embodiment will be described. In the α -sialon phosphor particles, a part of the raw material powder mainly reacts during the synthesis to form a liquid phase, and each element moves through the liquid phase, whereby solid solution formation and particle growth proceed.

First, raw materials containing elements constituting the Eu-containing α -type sialon phosphor particles are mixed. Specifically, in α -sialon phosphor particles synthesized using calcium nitride as a calcium raw material and having a low oxygen content, calcium is dissolved in a high concentration. In particular, when the Ca solid solution concentration is high, a phosphor having an emission peak wavelength on a higher wavelength side (590nm or more, more specifically, 590nm to 610nm, and even more specifically, 592nm to 608nm) than the conventional composition using an oxide raw material can be obtained. Specifically, in the above general formula, 1.5 < x + y + z.ltoreq.2.0 is preferable. It is also possible to substitute a part of Ca for Li, Mg, Sr, Ba, Y and lanthanoid (excluding La and Ce) and perform fine adjustment of the emission spectrum.

Examples of the raw material powder other than the above include silicon nitride, aluminum nitride, and Eu compound. Examples of the Eu compound include europium oxide, a compound which becomes europium oxide after heating, and europium nitride. Europium nitride is preferred to reduce the amount of oxygen in the system.

When an appropriate amount of α -sialon phosphor particles synthesized in advance is added to the raw material powder, these particles become the starting point of particle growth, α -sialon phosphor particles having a large minor axis diameter can be obtained, and the particle shape can be controlled by changing the form of the α -sialon particles added.

The above-mentioned raw materials may be mixed by a dry mixing method or a method of removing the solvent after wet mixing in an inert solvent which does not substantially react with the components of the raw materials. Examples of the mixing device include a V-type mixer, a swing type mixer, a ball mill, and a vibration mill. The mixing of calcium nitride, which is unstable in the atmosphere, is preferably performed in a glove box in an inert atmosphere because hydrolysis and oxidation thereof affect the characteristics of the resultant product.

The mixed powder (hereinafter, simply referred to as a raw material powder) is charged into a container made of a material having low reactivity with the raw material and the synthesized phosphor, for example, a container made of boron nitride. Then, the mixture was heated in a nitrogen atmosphere for a predetermined time. This gave an α -type sialon phosphor. The temperature of the heat treatment is preferably 1650 ℃ to 1950 ℃.

By setting the temperature of the heat treatment to 1650 ℃ or higher, the remaining amount of unreacted product can be suppressed, and primary particles can be sufficiently grown. Further, sintering between particles can be significantly suppressed by setting 1950 ℃ or lower.

From the viewpoint of suppressing sintering between particles during heating, it is preferable to increase the volume of the raw material powder filled in the container. Specifically, it is preferable that the bulk density of the raw material powder is 0.6g/cm when the container is filled with the raw material powder³The following.

The heating time in the heating treatment is preferably 2 to 24 hours, as a time range in which troubles such as the presence of a large amount of unreacted materials, insufficient primary particle growth, and sintering between particles do not occur.

The above steps produce an α -sialon phosphor in the form of an ingot. The secondary particles of the secondary particles-adjusted D can be obtained by subjecting the ingot-shaped α -sialon phosphor to a pulverizing step using a pulverizer such as a pulverizer, mortar pulverizing, ball mill, vibration mill or jet mill, and a screen classifying step after the pulverizing step₅₀A phosphor powder comprising α -sialon phosphor particles having a particle diameter. Further, by performing the step of dispersing the phosphor powder in the aqueous solution to remove the secondary particles having a small particle diameter and being less likely to settle, D of the secondary particles can be adjusted₅₀And (4) the particle size.

The phosphor powder composed of α -sialon phosphor particles according to the embodiment can be produced by performing the above-described steps and then performing an acid treatment step.

In the acid treatment step, for example, α -sialon phosphor particles are immersed in an acidic aqueous solution. Examples of the acidic aqueous solution include an acidic aqueous solution containing 1 acid selected from hydrofluoric acid, nitric acid, hydrochloric acid, and the like, and a mixed acid aqueous solution obtained by mixing 2 or more of the above acids. Among these, a hydrofluoric acid aqueous solution containing only hydrofluoric acid and a mixed acid aqueous solution obtained by mixing hydrofluoric acid and nitric acid are more preferable. The concentration of the stock solution of the acidic aqueous solution is appropriately set according to the strength of the acid used, and is, for example, preferably 0.7% to 100%, more preferably 0.7% to 40%. The temperature at the time of the acid treatment is preferably 25 to 90 ℃, more preferably 60 to 90 ℃, and the reaction time (immersion time) is preferably 15 to 80 minutes.

In the acid treatment step, the acidic aqueous solution is preferably stirred at a high speed. The acid treatment can be easily and sufficiently performed by high-speed stirring. The "high speed" here also depends on the stirring apparatus used, but when a laboratory-grade magnetic stirrer is used, the stirring speed is, for example, 400rpm or more, practically 400 to 500 rpm.

It is considered that from the viewpoint of a general purpose of stirring such as continuously supplying a new acid to the particle surface, a stirring speed of about 200rpm is sufficient. However, according to the findings of the present inventors, in the present embodiment, by performing high-speed stirring at 400rpm or more, it is possible to treat the particle surface by physical action in addition to chemical action. Further, it is considered that a phosphor powder having a diffuse reflectance of 93% to 99% with respect to light having a wavelength of 600nm can be easily obtained.

Median diameter (D) of phosphor powder₅₀) And the diffuse reflectance to light having a wavelength of 600nm can be controlled by optimally adjusting the degree of pulverization in the pulverization step, the mesh size of the sieve used in the sieve classification step, the stock solution concentration of the acidic aqueous solution used in the acid treatment, the temperature at the time of the acid treatment, the reaction time, and the like. For example, referring to various examples described later, the median particle diameter (D) of the phosphor powder can be adjusted by performing the acid treatment under conditions similar to the combination of the conditions of the pulverization step and the sieving step, the stock solution concentration of the acidic aqueous solution, the temperature at the time of the acid treatment, and the reaction time₅₀) And a diffuse reflectance to light having a wavelength of 600nm to a desired value.

(Complex)

The composite of the embodiment includes the phosphor particles and a sealing material for sealing the phosphor particles. In the composite of the present embodiment, a plurality of the above phosphor particles are dispersed in the sealing material. As the sealing material, a known material such as resin, glass, or ceramic can be used. Examples of the resin used for the sealing material include transparent resins such as silicone resin, epoxy resin, and urethane resin.

Examples of the method for producing the composite include the following methods: the phosphor particles of the present embodiment are prepared by adding a powder composed of α -sialon phosphor particles to a liquid resin or a powdery glass or ceramic, uniformly mixing the mixture, and then curing or sintering the mixture by heat treatment.

(light-emitting device)

Fig. 2 is a schematic cross-sectional view showing a structure of a light-emitting device according to an embodiment. As shown in fig. 2, the light-emitting device 100 includes a light-emitting element 120, a heat sink 130, a case 140, a first lead frame 150, a second lead frame 160, a bonding wire 170, a bonding wire 172, and a composite 40.

The light emitting element 120 is mounted on a predetermined region of the upper surface of the heat sink 130. By mounting the light emitting element 120 on the heat sink 130, the heat dissipation of the light emitting element 120 can be improved. Instead of the heat sink 130, a package substrate may be used.

The light emitting element 120 is a semiconductor element that emits excitation light. As the light emitting element 120, for example, an LED chip that generates light having a wavelength of 300nm to 500nm corresponding to near ultraviolet light to cyan light can be used. One electrode (not shown) disposed on the upper surface side of the light emitting element 120 is connected to the surface of the first lead frame 150 by a bonding wire 170 such as a gold wire. The other electrode (not shown) formed on the upper surface of the light-emitting element 120 is connected to the surface of the second lead frame 160 by a bonding wire 172 such as a gold wire.

The case 140 is formed with a substantially funnel-shaped recess portion whose aperture gradually increases from the bottom surface upward. The light emitting element 120 is provided on the bottom surface of the recess. The wall surface of the recess surrounding the light emitting element 120 functions as a reflection plate.

The composite 40 is filled in the recess formed in the wall surface of the case 140. The composite 40 is a wavelength conversion member that converts excitation light emitted from the light emitting element 120 into light of a longer wavelength. As the composite 40, the composite of the present embodiment is used, and the α -type sialon phosphor particles 1 of the present embodiment are dispersed in a sealing material 30 such as a resin. The light-emitting device 100 emits a mixed color of light from the light-emitting element 120 and light generated by the α -type sialon phosphor particles 1 that absorb and are excited by the light from the light-emitting element 120. The light-emitting device 100 preferably emits white light by mixing the light of the light-emitting element 120 and the light generated by the α -sialon phosphor particles 1.

In the light-emitting device 100 of the present embodiment, as described above, the phosphor powder composed of the α -sialon phosphor particles 1 satisfies the volume-based median particle diameter (D) measured by the laser diffraction scattering method₅₀) The conditions of 10 to 20 μm and the conditions of 93 to 99% diffuse reflectance to light having a wavelength of 600nm can both be satisfied, and the alpha-sialon phosphor particles 1 andthe fluorescent properties of the composite 40 further improve the light emission intensity of the light-emitting device 100.

Although fig. 2 shows a surface-mount light-emitting device, the light-emitting device is not limited to the surface-mount type. The light-emitting device may be of a shell type, a COB (chip on board) type, or a CSP (chip scale package) type.

While the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above may be adopted.

Examples

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

(example 1)

As the composition of the raw material powder, 62.4 parts by mass of silicon nitride powder (manufactured by Utsu Kagaku K.K., grade E10), 22.5 parts by mass of aluminum nitride powder (manufactured by Tokuyama Kagaku K., grade E), 2.2 parts by mass of europium oxide powder (manufactured by shin-Etsu chemical Co., Ltd., grade RU) and 12.9 parts by mass of calcium nitride powder (manufactured by high purity chemical research institute K.K.) were mixed together, and the mixture was dry-blended in a glove box, and then passed through a nylon sieve having a mesh size of 250. mu.m, to obtain a raw material mixed powder. 120g of this raw material mixed powder was charged into a cylindrical boron nitride container (N-1 grade, available from electrochemical Co., Ltd.) having an internal volume of 0.4 liter and a lid.

The raw material mixed powder was subjected to a heat treatment at 1800 ℃ for 16 hours in a nitrogen atmosphere of atmospheric pressure using an electric furnace of a carbon heater together with a vessel. Since calcium nitride contained in the raw material mixed powder is easily hydrolyzed in the air, the boron nitride container filled with the raw material mixed powder is taken out from the glove box, and then immediately placed in an electric furnace, and vacuum evacuation is performed to prevent the reaction of calcium nitride.

The resultant was lightly crushed with a mortar and the whole was passed through a sieve having a mesh opening of 150 μm to obtain a phosphor powder. The phosphor powder was examined for the crystal phase by powder X-ray Diffraction (X-ray Diffraction) using CuK alpha rays, and as a result, the crystal phase present was Ca-alpha sialon (Ca-containing alpha sialon) containing Eu.

Then, 3.2ml of 50% hydrofluoric acid and 0.8ml of 70% nitric acid were mixed to prepare a mixed stock solution. 396ml of distilled water was added to the mixed stock solution, and the concentration of the mixed stock solution was diluted to 1.0% to prepare 400ml of a mixed acid aqueous solution. 30g of the phosphor powder composed of the α -sialon phosphor particles was added to the mixed acid aqueous solution, and the mixed acid aqueous solution was immersed for 30 minutes while being stirred at a rotation speed of 450rpm by a magnetic stirrer while maintaining the temperature of 80 ℃. The acid-treated powder was thoroughly washed with distilled water and then filtered, and after drying, the powder was passed through a sieve having a mesh size of 45 μm to prepare phosphor powder composed of α -sialon phosphor particles of example 1.

(example 2)

Phosphor powder composed of α -type sialon phosphor particles of example 2 was prepared in the same manner as in example 1 except that 396ml of distilled water was added to a mixed stock solution obtained by mixing 1.2ml of 50% hydrofluoric acid and 2.8ml of 70% nitric acid instead of the mixed acid aqueous solution used in example 1 to prepare a mixed acid aqueous solution having a stock solution concentration of 1.0%.

(example 3)

A phosphor powder composed of α -type sialon phosphor particles of example 3 was produced in the same manner as in example 1, except that 380ml of distilled water was added to a mixed stock solution obtained by mixing 10ml of 50% hydrofluoric acid and 10ml of 70% nitric acid instead of the mixed acid aqueous solution used in example 1 to prepare a mixed acid aqueous solution having a stock solution concentration of 5.0%, and the phosphor powder was immersed for 30 minutes while maintaining the temperature of the mixed acid aqueous solution at 30 ℃.

(example 4)

A phosphor powder composed of α -type sialon phosphor particles of example 4 was produced in the same manner as in example 1, except that, instead of the mixed acid aqueous solution used in example 1, 300ml of distilled water was added to a mixed stock solution obtained by mixing 50ml of 50% hydrofluoric acid and 50ml of 70% nitric acid to prepare a mixed acid aqueous solution having a stock solution concentration of 25%, and the phosphor powder was immersed for 60 minutes while maintaining the temperature of the mixed acid aqueous solution at 80 ℃.

Comparative example 1

Phosphor powder composed of α -type sialon phosphor particles of comparative example 1 was prepared in the same manner as in example 1 except that 398ml of distilled water was added to a mixed stock solution obtained by mixing 1.0ml of 50% hydrofluoric acid and 1.0ml of 70% nitric acid to obtain a stock solution having a stock solution concentration of 0.5%, and that acid treatment was performed for 30 minutes while maintaining the temperature of the mixed acid aqueous solution at 80 ℃ and stirring the solution at a rotation speed of 300rpm with a magnetic stirrer, instead of the mixed acid aqueous solution used in example 1.

In the method for producing phosphor powder composed of α -sialon phosphor particles according to comparative example 1, the stock solution concentration of the mixed acid aqueous solution used for the acid treatment was set to a level conventionally practiced.

Comparative example 2

A phosphor powder composed of α -type sialon phosphor particles of comparative example 2 was produced in the same manner as in example 1 except that the mixture obtained in example 1 was lightly crushed in a mortar, then pulverized by a ball mill using zirconia balls having a diameter of Φ 1mm, and an aqueous mixed acid solution having a stock solution concentration of 25% obtained by adding 300ml of distilled water to a mixed stock solution obtained by mixing 50ml of hydrofluoric acid and 50ml of nitric acid 70 was used instead of the aqueous mixed acid solution used, and the phosphor powder was immersed for 60 minutes while maintaining the temperature of the aqueous mixed acid solution at 80 ℃.

(measurement of particle size)

The particle size was measured according to JIS R1629 using a Microtrac MT3300EX II (manufactured by Microtrac · Bel co., ltd.): 1997 by laser diffraction scattering. 0.5g of phosphor powder was put into 100cc of ion-exchanged water, and dispersed for 3 minutes by Ultrasonic Homogenizer US-150E (chip size. phi.20 mm, Amplified 100%, oscillation frequency 19.5KHz, Amplitude about 31 μm, manufactured by Nippon Seiko Co., Ltd.), and then the particle size was measured by MT3300EX II. Determining the median particle diameter (D) from the particle size distribution obtained₅₀). In addition, the volume-based cumulative 10% particle diameter (D) was determined₁₀) Volume-based cumulative 90% particle diameter (D)₉₀) Calculate (D)₉₀－D₁₀)/D₅₀. Results obtained for particle sizeShown in table 1.

(diffuse reflectance)

The diffuse reflectance was measured by mounting an integrating sphere device (ISV-722) on an ultraviolet-visible spectrophotometer (V-650) manufactured by Nippon spectral Co., Ltd. The base line was corrected with a standard reflection plate (Spectralon), a solid sample holder filled with phosphor powder was attached, and the diffuse reflectance was measured for light having wavelengths of 500nm, 600nm, 700nm and 800 nm. The results obtained for diffuse reflectance are shown in table 1.

(luminescent Property)

The internal quantum efficiency and the external quantum efficiency of each of the obtained phosphor powders were measured by a spectrophotometer (MCPD-7000, manufactured by Otsuka electronics Co., Ltd.) and calculated by the following procedure.

Phosphor powder was filled in such a manner that the surface of the concave cuvette was smooth, and an integrating sphere was attached. Monochromatic light split from a light emitting source (Xe lamp) into 455nm wavelength is introduced into the integrating sphere using an optical fiber. The sample of the phosphor powder is irradiated with the monochromatic light as an excitation source, and the fluorescence spectrum of the sample is measured.

A standard reflection plate (Spectralon, manufactured by Labsphere) having a reflectance of 99% was attached to the sample portion, and the spectrum of excitation light having a wavelength of 455nm was measured. At this time, the number of excitation photons is calculated from the spectrum in the wavelength range of 450nm to 465nm (Qex).

Phosphor powder composed of α -type sialon phosphor particles is attached to the sample portion, the peak wavelength is obtained from the obtained spectral data, and the number of photons of the excitation reflected light (Qref) and the number of photons of the fluorescence (Qem) are obtained. The number of photons of the excitation reflected light is calculated in the same wavelength range as the number of photons of the excitation light, and the number of photons of the fluorescence is calculated in the range of 465nm to 800 nm.

Internal quantum efficiency (Qem/(Qex-Qref)) × 100

External quantum efficiency (Qem/Qex). times.100

When the standard sample NSG1301 sold by Sialon corporation was measured by the above-mentioned measurement method, the external quantum efficiency was 55.6% and the internal quantum efficiency was 74.8%. The apparatus was calibrated using the sample as a standard. The results obtained for the internal and external quantum efficiencies are shown in table 1.

[ Table 1]

As shown in Table 1, it was confirmed that the median diameter (D) was satisfied₅₀) The phosphor powders of examples 1 to 4, which are the conditions of 10 to 20 μm and a diffuse reflectance of 93 to 99% for light having a wavelength of 600nm, have improved both internal and external quantum efficiencies as compared with comparative examples 1 and 2 which do not satisfy the conditions.

(additional embodiment)

Additional examples (experimental examples 1 and 2 below) show D₅₀The phosphor powder having a diffusion reflectance of 93 to 99% for light having a wavelength of 600nm and a diameter of 10 to 20 μm has excellent fluorescence characteristics.

Experimental example 1 is an example in which the acid treatment was intensified in examples 1 to 4, and Experimental example 2 is an example in which the raw material composition was slightly changed from that in examples 1 to 4.

Experimental example 1

As the composition of the raw material powder, 62.4 parts by mass of silicon nitride powder (manufactured by Utsu Kagaku K.K., grade E10), 22.5 parts by mass of aluminum nitride powder (manufactured by Tokuyama Kagaku K., grade E), 2.2 parts by mass of europium oxide powder (manufactured by shin-Etsu chemical Co., Ltd., grade RU) and 12.9 parts by mass of calcium nitride powder (manufactured by high purity chemical research institute K.K.) were mixed together, and the mixture was dry-blended in a glove box, and then passed through a nylon sieve having a mesh size of 250. mu.m, to obtain a raw material mixed powder. 120g of this raw material mixed powder was charged into a cylindrical boron nitride container (N-1 grade, available from electrochemical Co., Ltd.) having an internal volume of 0.4 liter and a lid.

The raw material mixed powder was heated at 1800 ℃ for 16 hours in a nitrogen atmosphere under atmospheric pressure by using an electric furnace having a carbon heater together with a vessel. Since calcium nitride contained in the raw material mixed powder is easily hydrolyzed in the air, the boron nitride container filled with the raw material mixed powder is taken out from the glove box, and then immediately placed in an electric furnace, and vacuum evacuation is performed to prevent the reaction of calcium nitride.

The resultant was lightly crushed with a mortar, and the whole was passed through a sieve having a mesh size of 150 μm to obtain a phosphor powder. The phosphor powder was examined for the crystal phase by powder X-ray Diffraction (X-ray Diffraction) using CuK alpha rays, and as a result, the crystal phase present was Ca-alpha sialon (Ca-containing alpha sialon) containing Eu.

Then, 100ml of 50% hydrofluoric acid and 100ml of 70% nitric acid were mixed to prepare a mixed stock solution. 200ml of distilled water was added to the mixed stock solution, and the concentration of the mixed stock solution was diluted to 50.0% to prepare 400ml of a mixed acid aqueous solution. 30g of the phosphor powder composed of the α -sialon phosphor particles was added to the mixed acid aqueous solution, and the mixed acid aqueous solution was immersed for 30 minutes while being stirred at a rotation speed of 450rpm by a magnetic stirrer while maintaining the temperature of 80 ℃. The acid-treated powder was thoroughly washed with distilled water and then filtered, and after drying, the powder was passed through a sieve having a mesh size of 45 μm to prepare phosphor powder composed of α -sialon phosphor particles of example 1.

Experimental example 2

As the composition of the raw material powder, 62.8 parts by mass of silicon nitride powder (manufactured by Utsu Kagaku K.K., grade E10), 22.7 parts by mass of aluminum nitride powder (manufactured by Tokuyama Kagaku K., grade E), 1.1 parts by mass of europium oxide powder (manufactured by shin-Etsu chemical Co., Ltd., grade RU) and 13.4 parts by mass of calcium nitride powder (manufactured by high purity chemical research institute K.K.) were mixed together, and the mixture was dry-blended in a glove box, and then passed through a nylon sieve having a mesh size of 250. mu.m, to obtain a raw material mixed powder. 120g of this raw material mixed powder was charged into a cylindrical boron nitride container (N-1 grade, available from electrochemical Co., Ltd.) having an internal volume of 0.4 liter and a lid.

The raw material mixed powder was heated at 1800 ℃ for 16 hours in a nitrogen atmosphere under atmospheric pressure by using an electric furnace having a carbon heater together with a vessel. Since calcium nitride contained in the raw material mixed powder is easily hydrolyzed in the air, the boron nitride container filled with the raw material mixed powder is taken out from the glove box, and then immediately placed in an electric furnace, and vacuum evacuation is performed to prevent the reaction of calcium nitride.

The resultant was lightly crushed with a mortar and the whole was passed through a sieve having a mesh opening of 150 μm to obtain a phosphor powder. The phosphor powder was examined for the crystal phase by powder X-ray Diffraction (X-ray Diffraction) using CuK alpha rays, and as a result, the crystal phase present was Ca-alpha sialon (Ca-containing alpha sialon) containing Eu.

Then, 3.2ml of 50% hydrofluoric acid and 0.8ml of 70% nitric acid were mixed to prepare a mixed stock solution. 396ml of distilled water was added to the mixed stock solution, and the concentration of the mixed stock solution was diluted to 1.0% to prepare 400ml of a mixed acid aqueous solution. 30g of the phosphor powder composed of the α -sialon phosphor particles was added to the mixed acid aqueous solution, and the mixed acid aqueous solution was immersed for 30 minutes while being stirred at a rotation speed of 450rpm by a magnetic stirrer while maintaining the temperature of 80 ℃. The acid-treated powder was thoroughly washed with distilled water and then filtered, and after drying, the powder was passed through a sieve having a mesh size of 45 μm to prepare phosphor powder composed of α -sialon phosphor particles of example 1.

The particle size, diffuse reflectance, and emission characteristics of the phosphor powder obtained were measured in the same manner as in examples 1 to 4.

The information relating to experimental examples 1 and 2 is summarized in table 2 below.

[ Table 2]

TABLE 2

As can be understood from the results of the additional examples: by changing the conditions and composition of the acid treatment by high-speed stirring, the diffuse reflectance can be adjusted to a value near 99%. The phosphor powder thus obtained has good fluorescence characteristics.

(additional experiment relating to the Change in acid treatment conditions and the accompanying Change in the final product)

Phosphor powder composed of α -type sialon phosphor particles was produced in the same manner as in example 2, except that the stirring speed with the magnetic stirrer was changed from 450rpm to 200rpm, which is a normal level, in example 2. The phosphor powder was subjected to particle size measurement, diffuse reflectance measurement, and evaluation of light emission characteristics in the same manner as in examples 1 to 4. The following table shows example 2, evaluation results, and the like.

[ Table 3]

TABLE 3

By changing the stirring speed of the acid treatment from 450rpm to 200rpm of example 2, the diffuse reflectance for light having a wavelength of 600nm was reduced from 94.8% to 93.5%. In addition, the difference between the diffuse reflectance at 800nm and the diffuse reflectance at 600nm increased from 2.2% to 3.1%.

That is, it can be understood from the additional experiment: by carefully setting the stirring conditions of the acid treatment, it is possible to obtain a phosphor powder having a large diffuse reflectance with respect to light having a wavelength of 600nm and/or a small difference between the diffuse reflectance at 800nm and the diffuse reflectance at 600 nm.

The present application claims priority based on japanese application No. 2019-069116, filed on 3/29/2019, the disclosure of which is incorporated herein in its entirety.

Description of the symbols

1 alpha-sialon phosphor particle

30 sealing Material

40 composite body

100 light emitting device

120 light emitting element

130 heat sink

140 casing

150 first lead frame

160 second lead frame

170 bonding wire

172 join line