阅读说明：本技术 荧光体粉末、复合体以及发光装置 (Phosphor powder, composite, and light-emitting device ) 是由 野见山智宏 武田雄介 山浦太阳 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。对于该荧光体粉末,将在大气气氛下在600℃保持1小时后的内量子效率设为P1、将在大气气氛下在700℃保持1小时后的内量子效率设为P2时,P1为70％以上,并且(P1－P2)/P1×100为2.8％以下。(One embodiment of the present invention is a phosphor powder composed of α -type sialon phosphor particles containing Eu. The phosphor powder has a P1 content of 70% or more and a (P1-P2)/P1X 100 content of 2.8% or less, where P1 represents the internal quantum efficiency after being maintained at 600 ℃ for 1 hour in an atmospheric atmosphere and P2 represents the internal quantum efficiency after being maintained at 700 ℃ for 1 hour in an atmospheric atmosphere.)

1. A phosphor powder comprising Eu-containing α -type sialon phosphor particles, wherein P1 is 70% or more and (P1-P2)/P1X 100 is 2.8% or less, where P1 represents the internal quantum efficiency after being held at 600 ℃ for 1 hour in an atmospheric atmosphere and P2 represents the internal quantum efficiency after being held at 700 ℃ for 1 hour in an atmospheric atmosphere.

2. The phosphor powder according to claim 1, wherein the internal quantum efficiency P2 is 68% or more.

3. The phosphor powder according to claim 1 or 2, wherein the internal quantum efficiency P3 after being held at 800 ℃ for 1 hour is 68% or more.

4. The phosphor powder according to any one of claims 1 to 3, wherein the emission spectrum is determined by the following [ extracted ion analysis A]The concentration C of the ammonium ion of the phosphor powder obtained_AIs 15ppm to 100ppm of the total amount of the catalyst,

[ extracted ion analysis A ]

0.5g of phosphor powder was put into 25mL of distilled water in a PTFE container with a cap, i.e., a polytetrafluoroethylene container,after 24 hours at 60 ℃, the total mass M of ammonia ions contained in the aqueous solution from which the solid content was removed by filtration was determined by ion chromatography_AThen, using M_ADividing by the mass of the phosphor powder to obtain C_A。

5. The phosphor powder according to any one of claims 1 to 4, wherein the diffuse reflectance for light having a wavelength of 600nm is 93% to 99%.

6. The phosphor powder according to any one of claims 1 to 5,

the alpha-sialon phosphor particle is represented by the general formula: (M1_x，M2_y，Eu_z)(Si _12－(m+n)Al _m+n)(O_nN _16－n) The Eu-containing alpha-sialon phosphor is characterized in that in the general formula, M1 is a 1-valent Li element, M2 is a 2-valent Ca element, x is 0-2.0, y is 0-2.0, z is 0-0.5, x + y is 0-0, x + y + z is 0.3-2.0, M is 0-4.0, and n is 0-3.0.

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 body is provided with: 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 a nitride or oxynitride phosphor, an α -sialon phosphor obtained by activating a specific rare earth element is known to have useful fluorescence characteristics, and is applied to a white LED and the like. In the α -sialon phosphor, the Si — N bond of the α -type silicon nitride crystal is partially substituted by Al — N bond and Al — O bond, and a specific element (Ca, Li, Mg, and Y, or a lanthanoid metal excluding La and Ce) is inserted into and dissolved in the crystal lattice in order to maintain electrical neutrality. The fluorescent property is exhibited by using a rare earth element as a part of the element which enters the solid solution and becomes a luminescence center. Among them, an α -sialon phosphor obtained by dissolving Ca in a solid solution and substituting a part thereof with Eu 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 strongly desired. For example, further improvement in light emission characteristics of phosphor powder for white LEDs is required.

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

According to the present invention, there is provided a phosphor powder comprising Eu-containing α -type sialon phosphor particles, wherein P1 is 70% or more and (P1-P2)/P1 × 100 is 2.8% or less, where P1 is the internal quantum efficiency after 1 hour at 600 ℃ in an atmospheric atmosphere and P2 is the internal quantum efficiency after 1 hour at 700 ℃ in an atmospheric atmosphere.

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 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 according to the embodiment is a phosphor powder composed of α -type sialon phosphor particles containing Eu. When the phosphor powder was held at 600 ℃ for 1 hour under an atmospheric atmosphere and the internal quantum efficiency was P1 and P2 after 1 hour at 700 ℃ under an atmospheric atmosphere, P1 was 70% or more and (P1-P2)/P1X 100 was 2.8% or less.

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 using the phosphor powder of the present embodiment can be improved.

For this reason, although the detailed mechanism is not yet established, it is presumed that the phosphor powder satisfying 70% or more of P1 and 2.8% or less of (P1-P2)/P1 × 100 has high surface chemical stability, and elements and compounds that do not contribute to fluorescence are sufficiently removed. Therefore, it is considered that the high fluorescence characteristics can be stably obtained even in a state where the heating is not performed.

(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 of 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 of 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, 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 of it is substituted with Eu, which is an emission center, and excited by light in a wide wavelength range from ultraviolet to cyan, thereby obtaining a phosphor exhibiting yellow to orange visible light emission.

In addition, from the viewpoint of obtaining light of a bulb color 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 has a second crystal phase different from that of the α -type sialon phosphor and an amorphous phase inevitably present, and therefore, a solid solution composition cannot be strictly defined by composition analysis or the like. The α -sialon phosphor is preferably an α -sialon single phase as a crystal phase, and aluminum nitride, a polytype thereof, or the like 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.

Average or median diameter (D) of particles of alpha-sialon phosphor₅₀) The lower limit of (B) is preferably 1 μm or more, more preferably 5 μm or more, and still more preferably 10 μm or more. Further, the average particle diameter or the median diameter (D) of the particles of the alpha-sialon phosphor₅₀) The upper limit of (B) is preferably 30 μm or less, more preferably 20 μm or less. Average particle diameter or median particle diameter (D) of alpha-sialon phosphor particles₅₀) Is the size of the secondary particles. By adjusting the average or median diameter (D) of the particles of the alpha-sialon phosphor₅₀) The transparency of the composite described later can be further improved by setting the thickness to 5 μm or more. On the other hand, the average particle diameter or the median diameter (D) of the particles of the alpha-sialon phosphor is determined₅₀) The particle size is 30 μm or less, so that generation of chips can be suppressed when the composite is cut and processed by a cutter or the like.

Here, the average particle size of the α -sialon phosphor particles is defined as follows based on JIS R1629: 1997 50% diameter of volume-based cumulative fraction by laser diffraction scattering method.

Here, the median diameter (D) of the phosphor powder₅₀) Means based on JIS R1629: 1997 median particle diameter (D) in volume-based cumulative fraction by laser diffraction scattering₅₀)。

The phosphor powder of the present embodiment has a P1 content of 70% or more and a (P1-P2)/P1 × 100 content of 2.8% or less, where P1 represents the internal quantum efficiency after being held at 600 ℃ for 1 hour in an atmospheric atmosphere, P2 represents the internal quantum efficiency after being held at 700 ℃ for 1 hour in an atmospheric atmosphere, and P3 represents the internal quantum efficiency after being held at 800 ℃ for 1 hour in an atmospheric atmosphere.

Here, the internal quantum efficiency of the phosphor powder can be measured by a spectrophotometer equipped with an integrating sphere.

The internal quantum efficiency after 1 hour of holding at each temperature described above can be regarded as an index of the chemical stability of the surface of the α -sialon phosphor particle. The indices defined by P1 and (P1-P2)/P1 × 100 of the phosphor powder of the present embodiment satisfy the above conditions, and the chemical stability of the surface is considered to be extremely high as compared with the conventional phosphor powder.

(P1-P2)/P1X 100 is more preferably 1.5% or less. This makes it possible to form phosphor powder having a surface with higher chemical stability.

In the phosphor powder of the present embodiment, it is preferable that P2 is 68% or more, except that the indices defined by P1 and (P1-P2)/P1 × 100 satisfy the above-described conditions. Accordingly, the chemical stability of the surface of the α -sialon phosphor particle can be further improved.

In addition to the above conditions, the phosphor powder of the present embodiment preferably has a P3 content of 68% or more. Accordingly, the chemical stability of the surface of the α -sialon phosphor particle can be further improved.

According to the phosphor powder described above, the fluorescent characteristics can be improved by satisfying the conditions that P1 is 70% or more and (P1-P2)/P1 × 100 is 2.8% or less.

(other characteristics)

The phosphor powder of the present embodiment preferably satisfies other characteristics in addition to the characteristics of P1, (P1-P2)/P1 × 100 described above.

As an example of the characteristics, the following [ extracted ion analysis A ] was used for phosphor powder]The concentration C of the ammonium ion of the phosphor powder obtained_APreferably 15ppm to 100ppm, more preferably 15ppm to 80ppm, and still more preferably 15ppm to 60 ppm.

Consider C_AIn particular, if the chemical stability of the surface of the phosphor particles is improved, the mother crystal of the phosphor contributing to fluorescence is likely to stably exist, and thus the fluorescence characteristics can be further improved.

[ extracted ion analysis A ]

0.5g of phosphor powder was put into 25mL of distilled water in a PTFE (polytetrafluoroethylene) container with a lid, and the mixture was held at 60 ℃ for 24 hours. Thereafter, the total mass M of ammonia ions contained in the aqueous solution from which the solid content was removed by filtration was determined by ion chromatography_A. Then, with M_ADividing by the mass of the phosphor powder to obtain C_A. I.e. C_AIs an index indicating the amount of ammonia ions per unit mass of the phosphor powder (solid state).

If the description is complemented, M_AThe ammonia ion concentration of the aqueous solution measured by ion chromatography can be multiplied by the mass (25g) of water used.

In addition, C_ABy using M_ADivided by the mass (0.5g) of the phosphor powder to be analyzed.

At M_AIn the case where the unit of (b) is "g (g)", C_A[ unit: ppm of]Can be obtained by using M_A[ unit: g]The value obtained by dividing the mass of the phosphor powder (0.5g) by 10⁶And then the result is obtained.

As another example of the characteristics, the diffusion reflectance of the phosphor powder with respect to light having a wavelength of 600nm is preferably 93% to 99%, more preferably 94% to 96%. The diffuse reflectance can be measured by an ultraviolet-visible spectrophotometer equipped with an integrating sphere device. The measurement method can be also referred to in the examples described later.

Diffuse reflectance is an index representing the degree of diffuse reflection of light. That is, the diffuse reflectance may be related to the surface state of the phosphor particles, the particle size distribution of the phosphor powder, and the like. The details are not clear, and it is estimated that the diffuse reflectance of the phosphor powder with respect to light having a wavelength of 600nm in the above numerical range indicates that, for example, a heterogeneous phase that does not contribute to fluorescence is sufficiently removed from the surface of the phosphor particles.

In the present embodiment, the median particle diameter D of the phosphor powder is preferable from the viewpoint of particularly good fluorescence characteristics (light emission efficiency and the like)₅₀10 to 20 μm and a wavelength of 600nmThe scattered reflectance is within the above numerical range.

(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 process 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. In alpha-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. Fine adjustment of the emission spectrum may also be performed by substituting a part of Ca for Li, Mg, Sr, Ba, Y, and lanthanoid (excluding La and Ce).

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 as the material which can reduce the amount of oxygen in the system.

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

As a method of mixing the above-mentioned raw materials, there are a dry mixing method, and a method of wet mixing in an inert solvent which does not substantially react with each component of the raw materials, and then removing the solvent. Examples of the mixing device include a V-type mixer, a swing type mixer, a ball mill, and a vibration mill. Mixing of calcium nitride, which is unstable in the atmosphere, is performed in a glove box in an inert atmosphere because hydrolysis and oxidation thereof affect the characteristics of the synthetic product.

The mixed powder (hereinafter, simply referred to as "raw material powder") is filled in 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. Subsequently, the mixture was heated in a nitrogen atmosphere for a predetermined time. Thus, an α -sialon phosphor was obtained. The temperature of the heat treatment is preferably 1650 ℃ to 1950 ℃.

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

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 heat treatment is preferably 2 to 24 hours, as a time range in which a large amount of unreacted materials, insufficient primary particle growth, or sintering between particles does not occur.

The above-described steps produce an α -sialon phosphor having an ingot-like outer shape. The secondary particles of the secondary particles-adjusted D can be obtained by subjecting the ingot-shaped α -sialon phosphor to a pulverization step using a pulverizer such as a crusher, mortar mill, ball mill, vibration mill or jet mill, and a sieve classification step after the pulverization step₅₀A phosphor powder comprising α -sialon phosphor particles having a particle diameter. Further, the step of dispersing the dispersion in an aqueous solution to remove secondary particles having a small particle diameter and being less likely to settle can be performed to adjust D of the secondary particles₅₀And (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 hydrofluoric acid alone and a mixed acid aqueous solution obtained by mixing hydrofluoric acid and nitric acid are more preferable. The stock solution concentration 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.

A preferred embodiment of the acid treatment step is a method in which the phosphor powder is added to an acidic solution and then stirred for a predetermined time. Thus, the reaction with the acid can be more reliably performed on the surface of the α -sialon phosphor particles. By stirring at a high speed, the acid treatment of the particle surface can be easily and sufficiently performed. 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, and in reality, 400rpm to 500 rpm. If the stirring speed is about 200rpm for the purpose of ordinary stirring in which a new acid is continuously supplied to the particle surface, it is considered that the stirring speed is sufficient, and when the stirring is performed at a high speed of 400rpm or more, elements and compounds that do not contribute to fluorescence are sufficiently removed by physical action in addition to chemical action, and/or the chemical stability of the particle surface is improved.

As described above, the conditions defined for the internal quantum efficiency after the heat treatment, under which P1 is 70% or more and (P1-P2)/P1 × 100 is 2.8% or less, can be controlled by optimally adjusting the stock solution concentration of the acidic aqueous solution used for the acid treatment, the temperature at the time of the acid treatment, the reaction time, the stirring speed, and the like. For example, with reference to the examples described later, the phosphor powder can be made to have desired values of P1 and (P1-P2)/P1X 100 by performing the acid treatment under conditions similar to the combination of the stock solution concentration of the acidic aqueous solution, the temperature at the time of the acid treatment, the reaction time, and the stirring speed.

(Complex)

The composite according to the embodiment includes the phosphor particles and a sealing material for sealing the phosphor particles. In the composite according to the present embodiment, a plurality of the phosphor particles are dispersed in the sealing material. As the sealing material, known materials such as resin, glass, and ceramics 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. 1 is a schematic cross-sectional view showing a structure of a light-emitting device according to an embodiment. As shown in fig. 1, 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. In addition, a substrate for package may be used instead of the heat sink 130.

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 light from near ultraviolet to cyan 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 via 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 via a bonding wire 172 such as a gold wire.

The housing 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 surrounding the recess of the light emitting element 120 functions as a reflection plate.

The composite 40 is filled in the recess formed in the wall surface by 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 from the α -type sialon phosphor particles 1 excited by absorbing 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 from the α -sialon phosphor particles 1.

In the light-emitting device 100 of the present embodiment, as described above, when the internal quantum efficiency of the phosphor powder composed of the α -sialon phosphor particles 1 after being held at 600 ℃ for 1 hour in the atmospheric atmosphere is P1 and the internal quantum efficiency after being held at 700 ℃ for 1 hour in the atmospheric atmosphere is P2, P1 is 70% or more and (P1-P2)/P1 × 100 is 2.8% or less, the fluorescence characteristics of the α -sialon phosphor particles 1 and the composite 40 are improved, and the light emission intensity of the light-emitting device 100 can be improved.

Fig. 1 illustrates a surface-mount type light emitting device, and the light emitting device is not limited to the surface-mount type. The light emitting device may be a shell type, a COB (chip on board) type, 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-described configurations may be adopted.

Examples

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

(example 1)

The raw material powders were mixed in a glove box with 62.4 parts by mass of silicon nitride powder (manufactured by yukexing corporation, E10 grade), 22.5 parts by mass of aluminum nitride powder (manufactured by TOKUYAMA corporation, E grade), 2.2 parts by mass of europium oxide powder (manufactured by shin-Etsu chemical Co., Ltd., RU grade), and 12.9 parts by mass of calcium nitride powder (manufactured by high purity chemical research Co., Ltd.), and the mixture was sieved with a nylon mesh of 250 μm 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, manufactured by electrochemical Co., Ltd.) with a lid having an internal volume of 0.4 liter.

The raw material mixed powder was subjected to a heating treatment for 16 hours at 1800 ℃ in a nitrogen atmosphere of atmospheric pressure in 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 quickly set in an electric furnace, and vacuum evacuation is immediately 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 (hereinafter, referred to as XRD measurement) using CuK α rays, and as a result, the crystal phase existing was Ca — α sialon (Ca-containing α sialon) containing Eu element.

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 described above was added to the mixed acid aqueous solution, and the mixture was immersed in a 500ml beaker for 30 minutes while being stirred at a rotation speed of 450rpm using a magnetic stirrer with the temperature of the mixed acid aqueous solution being maintained at 80 ℃. The acid-treated powder was thoroughly washed with distilled water and filtered, and then dried, followed by passing 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)

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 in the mixed acid aqueous solution at 30 ℃ for 30 minutes.

(example 4)

Phosphor powder composed of α -type sialon phosphor particles of example 4 was prepared in the same manner as in example 1 except that 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 instead of the mixed acid aqueous solution used in example 1 to prepare a 25% stock solution mixed acid aqueous solution, and the phosphor powder was immersed in the mixed acid aqueous solution at 80 ℃ for 60 minutes.

Comparative example 1

Phosphor powder composed of α -type sialon phosphor particles of comparative example 1 was prepared in the same procedure 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 the temperature of the mixed acid aqueous solution was maintained at 80 ℃ in a 500ml beaker, and that the mixed acid aqueous solution was immersed for 30 minutes while being stirred at a rotation speed of 300rpm using a magnetic stirrer, instead of the mixed acid aqueous solution used in example 1.

The stock solution concentration and the stirring rotation speed of the mixed acid aqueous solution used in comparative example 1 were set to the levels conventionally practiced.

(measurement of particle size)

The particle size was measured by using a Microtrac MT3300EX II (Microtrac · Bel co., ltd.) and by adjusting the particle size according to JIS R1629: 1997 by laser diffraction scattering. 0.5g of phosphor powder was put into 100cc of ion-exchanged water, and the resultant mixture was treated with an Ultrasonic Homogenizer US-150E (Japan K.K.)Chip size Φ 20, Amplitude 100%, oscillation frequency 19.5KHz, Amplitude about 31 μm) was subjected to dispersion treatment for 3 minutes by finisher, and thereafter, particle size measurement was performed using MT3300EX II. Determining the median particle diameter (D) from the particle size distribution obtained₅₀)。

(luminescent Property)

The internal quantum efficiency and the external quantum efficiency at room temperature of each of the obtained phosphor powders were measured by a spectrophotometer (MCPD-7000, manufactured by Otsuka electronics Co., Ltd.), and the calculation was performed in the following order.

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 was attached to the sample portion, and the number of photons of excitation reflected light (Qref) and the number of photons of fluorescence (Qem) were calculated. 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 this sample as a standard.

The internal quantum efficiencies after the heat treatment under the following 3 conditions were independently measured.

(1) The phosphor powder was held at 600 ℃ for 1 hour, and the internal quantum efficiency P1 was measured

(2) The phosphor powder was held at 700 ℃ for 1 hour, and then the internal quantum efficiency P2 was measured

(3) The phosphor powder was held at 800 ℃ for 1 hour, and the internal quantum efficiency P3 was measured

The conditions for the respective heat treatments are as follows.

High temperature ambient furnace (atmosphere)

Sample holding method: closed type (holding sample in aluminum container with lid having inner volume of 30 cc)

(P1-P2)/P1X 100 (%) was calculated using the obtained P1 and P2. The results obtained for the internal and external quantum efficiencies are shown in table 1.

The peak wavelengths of the emission spectra of the phosphor powders obtained by the above measurement (excitation light wavelength: 455nm) were all 600nm (large wavelength) in examples 1 to 4.

(concentration C of ammonium ion in phosphor powder)_AMeasurement of (2)

The concentration C of ammonia ions in the phosphor powder of example 2 was measured in the following manner_A。

0.5g of phosphor powder was put into 25ml of distilled water in a PTFE container with a lid. The vessel containing the phosphor powder and distilled water was kept at 60 ℃ for 24 hours, and then the solid content was removed by filtration. The concentration of ammonia ions in the aqueous solution from which the solid matter was removed was measured by an ion chromatography apparatus (manufactured by Thermo Fisher Scientific Co., Ltd.), and the total mass M of eluted ammonia ions was determined from the concentration and the amount of the aqueous solution_A(unit: g). Then, with M_ADivided by the mass of phosphor powder (0.5g), multiplied by 10⁶Thus, the concentration C of the ammonium ion in the phosphor powder was determined_A(unit: ppm).

(measurement of diffusion reflectance of phosphor powder)

The diffusion reflectance at a wavelength of 600nm of the phosphor powder of example 2 was measured in the following manner.

The diffuse reflectance was measured by mounting an integrating sphere device (ISV-722) in an ultraviolet-visible spectrophotometer (V-650) manufactured by Nippon spectral Co., Ltd. The base line was corrected by a standard reflection plate (Spectralon), a solid sample holder filled with a phosphor powder was mounted, and the diffuse reflectance for light having a wavelength of 600nm was measured.

Table 1 summarizes various information on examples and comparative examples.

Although not shown in Table 1, the phosphor powder of example 2 had an ammonia ion concentration C_AWas 29 ppm. The phosphor powder of example 2 had a diffuse reflectance at a wavelength of 600nm of 94.8%.

[ Table 1]

As shown in Table 1, it was confirmed that the phosphor powders of examples 1 to 4 satisfying the conditions that P1 was 70% or more and (P1-P2)/P1X 100 was 2.8% or less exhibited improved internal and external quantum efficiencies as compared with comparative example 1 not satisfying the conditions.

(additional comparative example: example in which the acid treatment conditions were changed in example 2)

Phosphor powder composed of α -sialon phosphor particles was obtained in the same manner as in example 2, except that the stirring speed by a magnetic stirrer in the acid treatment was changed from 450rpm to 200rpm, which is a normal level.

The median diameter D of the phosphor powder obtained in this additional comparative example₅₀14.5 μm, a diffuse reflectance at a wavelength of 600nm of 93.5%, and a concentration C of ammonia ions in the phosphor powder_AWas 113 ppm.

The phosphor powder obtained in the additional comparative example had an internal quantum efficiency of 75.4% and an external quantum efficiency of 66.6%, which was inferior to that of example 2 (and other examples).

As can be understood from the results of the above additional comparative examples and the like:

the final phosphor powder was different between the case of "high-speed stirring" at a stirring speed of 450rpm in the acid treatment (example 2) and the case of "low-speed stirring" at 200rpm,

the phosphor powder obtained by low-speed stirring has poor light emission characteristics.

The present application claims priority based on japanese application No. 2019-069109, filed on 3/29/2019, the entire disclosure of which is incorporated herein by reference.

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