阅读说明：本技术 荧光体粉末和发光装置 (Phosphor powder and light-emitting device ) 是由 小林学 野见山智宏 于 2020-04-15 设计创作，主要内容包括：本发明的一个方案是包含Eu活化了的β型塞隆荧光体粒子作为主要成分的荧光体粉末。一种荧光体粉末,对于未实施超声波均化器处理的上述荧光体粉末,将通过使用了激光衍射式粒度分布测定装置的湿式测定而测得的中值径(D-(50))设为D1,对于实施了以以下条件实施的超声波均化器处理的上述荧光体粉末,将通过使用了激光衍射式粒度分布测定装置的湿式测定而测得的中值径(D-(50))设为D2,此时,D1/D2为1.05～1.70。(条件)使上述荧光体粉末30mg均匀分散于浓度0.2％六偏磷酸钠水溶液100ml中而得到分散液,将该分散液放入底面为内径5.5cm的圆柱状容器。接着,在将超声波均化器的外径20mm的圆柱状芯片浸入该分散液中1.0cm以上的状态下,以频率19.5kHz、输出150W对该分散液照射超声波3分钟。(One embodiment of the present invention is a phosphor powder containing Eu-activated β -type sialon phosphor particles as a main component. A phosphor powder, wherein the phosphor powder which has not been subjected to an ultrasonic homogenizer treatment has a median diameter (D) measured by wet measurement using a laser diffraction particle size distribution measuring apparatus 50 ) D1 represents the median diameter (D) of the phosphor powder subjected to the ultrasonic homogenizer treatment under the following conditions, which was measured by wet measurement using a laser diffraction particle size distribution measuring apparatus 50 ) D2, wherein D1/D2 is 1.05-1.70. (Condition) 30mg of the phosphor powder was uniformly dispersed in a 0.2% aqueous solution of sodium hexametaphosphate100ml of the dispersion was poured into a cylindrical container having an inner diameter of 5.5cm on the bottom. Next, ultrasonic waves were irradiated to the dispersion at a frequency of 19.5kHz and an output of 150W for 3 minutes in a state where a cylindrical chip having an outer diameter of 20mm of an ultrasonic homogenizer was immersed in the dispersion for 1.0cm or more.)

1. A phosphor powder comprising Eu-activated beta-sialon phosphor particles as a main component,

for not implementingThe phosphor powder treated with the ultrasonic homogenizer has a median diameter D measured by wet measurement using a laser diffraction particle size distribution measuring apparatus₅₀The setting is that the D1 is set,

the median diameter D measured by wet measurement using a laser diffraction particle size distribution measuring apparatus was measured for the phosphor powder subjected to the ultrasonic homogenizer treatment under the following conditions₅₀The setting is that the D2 is set,

in this case, D1/D2 is 1.05-1.70;

conditions are as follows:

30mg of the phosphor powder was uniformly dispersed in 100ml of a 0.2% aqueous solution of sodium hexametaphosphate to obtain a dispersion, the dispersion was placed in a cylindrical container having an inner diameter of 5.5cm on the bottom surface, and then a cylindrical chip having an outer diameter of 20mm of an ultrasonic homogenizer was immersed in the dispersion for 1.0cm or more, and the dispersion was irradiated with ultrasonic waves at a frequency of 19.5kHz and an output of 150W for 3 minutes.

2. The phosphor powder according to claim 1, wherein D1 is 10 to 35 μm.

3. The phosphor powder according to claim 1 or 2, wherein the D2 is 8 to 25 μm.

4. A light-emitting device is provided with:

a light emitting element, and

a wavelength converting region using the phosphor powder according to any one of claims 1 to 3.

Technical Field

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

Background

In recent years, a light-emitting device has been developed in which a semiconductor light-emitting element such as an LED and a phosphor that absorbs a part of light from the semiconductor light-emitting element and converts the absorbed light into wavelength-converted light having a long wavelength to emit light are combined. As the phosphor, a nitride phosphor and an oxynitride phosphor having a relatively stable crystal structure have attracted attention. In particular, since a Eu-activated β -sialon phosphor is excited by light having a wide wavelength from ultraviolet to blue light and emits green light having a peak in a wavelength region of 520 to 550nm, in addition to the characteristics of excellent heat resistance and durability and small change in luminance accompanying temperature rise, the Eu-activated β -sialon phosphor has been advanced as a practical application to a phosphor useful for a white LED (see patent document 1).

For example, patent document 2 discloses a β -type sialon phosphor having an average particle size (D1) (air transmission method) of 9 to 16 μm, a median diameter (50% D) in the particle size distribution of 12.5 to 35 μm, and satisfying the condition that 50% D/D1 is 1.4 to 2.2.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2010/143590

Patent document 2: international publication No. 2011/083671

Disclosure of Invention

In recent years, with the increasing demand for white LEDs, further enhancement of luminance has been demanded, and the level of demand for the characteristics of β -type sialon phosphors used in white LEDs has been increasing.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique relating to a β -type sialon phosphor capable of improving the luminance of a white LED.

According to the present invention, there is provided a phosphor powder comprising Eu-activated beta-sialon phosphor particles as a main component,

for the above phosphor powder which has not been subjected to the ultrasonic homogenizer treatment, the phosphor powder is prepared byMedian diameter (D) measured by wet measurement using a laser diffraction particle size distribution measuring apparatus₅₀) The setting is that the D1 is set,

the median diameter (D) of the phosphor powder subjected to the ultrasonic homogenizer treatment under the following conditions was measured by wet measurement using a laser diffraction particle size distribution measuring apparatus₅₀) The setting is that the D2 is set,

in this case, D1/D2 is 1.05 to 1.70.

(Condition)

30mg of the phosphor powder was uniformly dispersed in 100ml of a 0.2% aqueous solution of sodium hexametaphosphate to obtain a dispersion, and the dispersion was placed in a cylindrical container having a bottom surface with an inner diameter of 5.5 cm. Next, ultrasonic waves were irradiated to the dispersion at a frequency of 19.5kHz and an output of 150W for 3 minutes in a state where a cylindrical chip having an outer diameter of 20mm of an ultrasonic homogenizer was immersed in the dispersion for 1.0cm or more.

Further, according to the present invention, there is provided a light-emitting device including the light-emitting element and the phosphor powder.

According to the phosphor powder of the present invention, the luminance of a white LED can be improved.

Detailed Description

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

The present inventors investigated the relationship between the aggregation state of Eu-activated β -type sialon phosphor particles and the luminance of a white LED using the phosphor particles, and as a result, found that the ratio of the median diameter of the phosphor particles before and after the ultrasonic homogenizer treatment is closely related to the luminance of a white LED using the phosphor. The present inventors have not studied about the conventional Eu-activated β -type sialon phosphor particles in adjusting the ratio of median diameters before and after the ultrasonic homogenizer treatment, and have thought that there is room for improving the luminance of a white LED by controlling the degree of aggregation of the phosphor particles, and have completed the present invention.

The phosphor powder of the embodiment contains Eu-activated β -type sialon phosphor particles (hereinafter, may be simply referred to as "phosphor particles") as a main component. The main component here means that the Eu-activated β -type sialon phosphor particles are contained by 90 mass% or more with respect to the entire phosphor powder. In this case, the phosphor powder may contain phosphor particles other than Eu-activated β -type sialon phosphor particles.

The phosphor powder of the present embodiment is composed of Eu-activated β -type sialon phosphor particles, and in other words, the content of Eu-activated β -type sialon phosphor particles is preferably 100 mass%.

The composition of the Eu-activated β -sialon phosphor particles of the present embodiment is represented by the general formula: si_6－zAl_zO_zN_8－zDivalent europium (Eu) is dissolved in beta-sialon expressed by (z is 0.005-1)²⁺) A phosphor obtained as a light emission center.

The phosphor powder of the embodiment contains Eu-activated β -type sialon phosphor particles as a main component, and the median diameter (D) measured by wet measurement using a laser diffraction particle size distribution measuring apparatus is used for the phosphor powder not subjected to the ultrasonic homogenizer treatment₅₀) D1 represents the median diameter (D) of the phosphor powder subjected to the ultrasonic homogenizer treatment under the following conditions, which was measured by wet measurement using a laser diffraction particle size distribution measuring apparatus₅₀) D2, wherein D1/D2 is 1.05-1.70.

(Condition)

30mg of the phosphor powder was uniformly dispersed in 100ml of a 0.2% aqueous solution of sodium hexametaphosphate to obtain a dispersion, and the dispersion was placed in a cylindrical container having a bottom surface with an inner diameter of 5.5 cm. Next, ultrasonic waves were irradiated to the dispersion at a frequency of 19.5kHz and an output of 150W for 3 minutes in a state where a cylindrical chip having an outer diameter of 20mm of an ultrasonic homogenizer was immersed in the dispersion for 1.0cm or more.

The phosphor powder of the present embodiment is processed by the ultrasonic homogenizer under the above-described specific conditions to deagglomerate phosphor particles and to monodisperse the particles. In other words, the phosphor powder of the present embodiment is a powder in which phosphor particles are appropriately aggregated. In addition, since almost no aggregation occurs, the state is close to a monodisperse state, D1 and D2 are almost the same, and D1/D2 are close to 1, even if the particles are dispersed by the ultrasonic homogenizer treatment under the above-mentioned specific conditions. When the degree of aggregation of the phosphor particles is too large, the number of phosphor particles that are deagglomerated and monodispersed by the ultrasonic homogenizer treatment under the above-described specific conditions increases, and thus D1/D2 increases.

When the phosphor powder of the present embodiment has a D1/D2 of 1.05 or more, the luminance of a white LED using the phosphor powder can be improved. On the other hand, when D1/D2 is 1.70 or less, aggregation of particles is suppressed, and thus dispersibility in a white LED sealing material described later is improved, and a decrease in luminance is suppressed.

As described in patent documents 1 and 2, the aggregated state of the phosphor powder is almost unchanged even when the phosphor powder composed of β -type sialon phosphor particles of a general technical level is subjected to the ultrasonic homogenizer treatment. That is, it can be said that the aggregation is hardly caused. In contrast, the phosphor powder of the present embodiment is regulated to have D1/D2 in a specific range, and the phosphor powder is appropriately aggregated, whereby the total luminous flux when the phosphor powder of the present embodiment is used for a white LED can be increased.

The dispersion under the above conditions can be obtained as follows: 30mg of the phosphor powder and 100ml of an aqueous solution of sodium hexametaphosphate adjusted to 0.2% were collected in a 200ml beaker, and then stirred uniformly at room temperature (25 ℃) to such an extent that no precipitation occurs, using a spatula.

The median diameter (D) of the phosphor powder₅₀) Specifically, the calculation was performed by a wet measurement method or a flow cell method using a laser diffraction particle size distribution measuring apparatus. At this time, the powder was supplied to the measuring apparatus without applying ultrasonic waves, and the Sample was supplied at a pump flow rate of 75% by using the attached SDC (Sample Delivery Controller) as a Sample supplier, and the measurement was performed. As the dispersion medium, an aqueous solution of sodium hexametaphosphate adjusted to 0.2% was used.

The lower limit of D1/D2 is preferably 1.10 or more, more preferably 1.15 or more, and still more preferably 1.20 or more. On the other hand, D1/D2 is preferably 1.65 or less, more preferably 1.55 or less. When the lower limit and the upper limit of D1/D2 are set to the above ranges, the luminance of a white LED using the phosphor powder can be further improved.

The lower limit of D1 is preferably 10 μm or more, more preferably 13 μm or more, and still more preferably 16 μm or more. The upper limit of D1 is preferably 35 μm or less, more preferably 32 μm or less, and still more preferably 29 μm or less. When the lower limit and the upper limit of D1 are set to the above ranges, the luminance of a white LED using the phosphor powder can be further improved.

The lower limit of D2 is preferably 8 μm or more, more preferably 11 μm or more, and still more preferably 14 μm or more. The upper limit of D2 is preferably 25 μm or less, more preferably 22 μm or less, and still more preferably 19 μm or less. When the lower limit and the upper limit of D2 are set to the above ranges, the luminance of a white LED using the phosphor powder can be further improved.

The median diameter (D) of the phosphor powder according to the embodiment measured by wet measurement using a laser diffraction particle size distribution measuring apparatus₁₀) Preferably 7.0 to 25 μm, and more preferably 9.5 to 20 μm.

The median diameter (D) of the phosphor powder according to the embodiment measured by wet measurement using a laser diffraction particle size distribution measuring apparatus₉₀) Preferably 20 to 60 μm, and more preferably 25 to 55 μm.

By making the median diameter (D) of the phosphor powder of the embodiment₁₀) Median diameter (D)₉₀) Within the above numerical range, variations in the phosphor powder can be suppressed, and the luminance of a white LED using the phosphor powder can be further improved.

(method for producing phosphor powder)

The method for producing the phosphor powder of the present embodiment includes, for example, a mixing step, a first firing step, a second firing step, a crushing/pulverizing step, an annealing step, an acid treatment step, and a cleaning/filtering step as described below. The D1/D2 is realized by adjusting the filling method (filling density), temperature reduction rate, and the like in the annealing step by appropriately combining the above steps.

< mixing Process >

In the mixing step, for example, a silicon compound such as silicon nitride, an aluminum compound such as aluminum nitride or aluminum oxide, and an Eu compound (collectively referred to as a raw material compound) selected from Eu metal, oxide, carbonate, halide, nitride, or oxynitride are weighed and mixed so as to constitute the phosphor powder of the present embodiment, thereby preparing a raw material mixture. The method for mixing the raw material compounds is not particularly limited, but examples thereof include the following methods: mixing is performed using a known mixing device such as a V-type mixer, and further, sufficient mixing is performed using a mortar, a ball mill, a planetary mill, a jet mill, or the like. When europium nitride or the like which reacts vigorously with moisture and oxygen in the air is mixed, the treatment is preferably performed in a glove box which is replaced with an inert atmosphere.

The aluminum compound may be 1 or more aluminum compounds selected from aluminum-containing compounds that decompose by heating to produce aluminum oxide.

< first firing Process >

The raw material mixed powder is charged into a container such as a crucible in which at least the surface in contact with the raw material is made of boron nitride, and the inside of the raw material powder is reacted by heating at a temperature of 1550 to 2100 ℃ in a nitrogen atmosphere. The first firing step is intended to highly disperse Eu in the mixed powder by reaction, and the degree of the formation rate is not limited as long as β -type sialon is partially formed at this stage. Eu is highly dispersed by diffusion in a liquid phase generated when the oxides contained in the raw materials become high temperature. By setting the firing temperature to 1550 ℃ or higher, the amount of the liquid phase present can be made sufficient, and the diffusion of Eu can be made sufficient. Setting the firing temperature to 2100 ℃ or lower eliminates the need for a very high nitrogen pressure for suppressing the decomposition of the β -sialon, and is therefore industrially preferred. The firing time in the first firing step also depends on the firing temperature, but is preferably adjusted within a range of 2 to 18 hours.

The sample (first fired powder) obtained in the first firing step is in the form of powder or block depending on the raw material mixture composition and firing temperature. Therefore, if necessary, the mixture is crushed and pulverized into a powder having a mesh size of, for example, 45 μm.

< second firing Process >

Next, at least one selected from the group consisting of silicon nitride, silicon oxide, aluminum nitride, aluminum oxide, and europium oxide is added to the first fired powder, mixed by the same method as in the mixing step, filled in a container, and subjected to a second firing step at a temperature of 1900 to 2100 ℃ in a nitrogen atmosphere to obtain Eu-solid solution β -sialon. In the second firing step, a firing temperature of 1900 ℃ or higher is preferable in order to increase the formation rate of β -sialon. The firing time in the second firing step also depends on the firing temperature, but is preferably adjusted in the range of 6 to 18 hours.

< crushing/pulverizing Process >

Since the sample after the second firing step (second fired powder) is in a block shape, a classification operation is combined as necessary to prepare a powder having a predetermined size at the time of crushing. As a specific example of the processing operation, the following method can be cited: a method of crushing and pulverizing the second calcined powder and classifying the crushed powder by a sieve in a mesh size range of 20 to 45 μm to obtain a powder passing through the sieve, or a method of pulverizing the second calcined powder into a predetermined particle size by using a general pulverizer such as a ball mill, a vibration mill, or a jet mill. When a pulverizer is used, it is preferable to use a pulverizing apparatus and pulverizing conditions that are as gentle as possible so as not to mechanically damage the second calcined powder.

In the above-described pulverization treatment, the member of the pulverizing apparatus which comes into contact with the second calcined powder as the object to be pulverized is preferably made of high-toughness ceramics such as silicon nitride, alumina, sialon and the like in order to prevent the impurity element from being mixed. From the viewpoint of obtaining a oxynitride phosphor for an LED that exhibits high absorption efficiency of excitation light and sufficient emission efficiency, the second calcined powder that has been subjected to the crushing/pulverization step is preferably adjusted to a powder having an average particle size of 50 μm or less.

< annealing Process >

The Eu-activated beta-sialon powder synthesized by the above method is mixed with a solvent other than pure nitrogenAnnealing at a temperature lower than that in the second firing step in a non-oxidizing atmosphere to increase Eu²⁺The ratio of Eu is such that Eu, which inhibits fluorescence, is changed to a state that can be dissolved and removed by acid treatment in the next step. The atmosphere in which the annealing treatment is performed is preferably a rare gas or a reducing gas. The rare gas is a gas of a group 18 element such as argon or helium. The reducing gas is, for example, a gas having a reducing power such as ammonia, carbon dioxide, carbon monoxide, or hydrogen. The reducing gas may be used as a single body, or may be a mixed gas with a neutral gas such as nitrogen or a rare gas.

The temperature of the annealing treatment is suitably varied depending on the atmosphere used. If the temperature is too low, no change in the state of Eu occurs, and the characteristics are not improved, whereas if the temperature is too high, β -sialon is decomposed, which is not preferable. The temperature range suitable for annealing in a rare gas atmosphere such as argon or helium is 1350 to 1600 ℃. The annealing time in the annealing step also depends on the annealing temperature, but is preferably adjusted within a range of 4 hours to 12 hours.

From the viewpoint of setting D1/D2 to an appropriate value, when the annealing treatment is performed, it is preferable to fill a vessel with a lid (such as a crucible whose surface in contact with the raw material is made of boron nitride) with Eu-activated β -type sialon powder by tapping (tapping), thereby appropriately increasing the filling level. The degree of filling may be, for example, a close state in which Eu-activated β -sialon powder is in contact with the lid.

From the viewpoint of setting the above D1/D2 to an appropriate value, it is preferable to cool the Eu-activated β -sialon powder after annealing at a temperature lowering rate higher than conventional levels. The cooling conditions include a temperature reduction of preferably 3 to 10 ℃/min in a temperature range of 1000 to 1500 ℃, and a temperature reduction of more preferably 4 to 6 ℃/min in the above temperature range.

< acid treatment Process >

Next, the annealed β -type sialon powder is subjected to an acid treatment. As the acid used for the acid treatment, 1 or 2 or more acids selected from hydrofluoric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid are used, and these acids are used in the form of an aqueous solution containing these acids. The acid treatment is mainly intended to remove a compound which inhibits fluorescence or luminescence generated during the annealing treatment, and a mixed acid of hydrofluoric acid and nitric acid is preferably used. The acid treatment process was carried out as follows: the annealed β -sialon powder is dispersed in an aqueous solution containing the acid, and is stirred for several minutes to several hours (for example, 10 minutes to 3 hours) to react with the acid. The temperature of the acid may be room temperature, but the reaction proceeds more easily as the temperature is higher, and therefore, it is preferably 50 to 80 ℃.

< cleaning/filtration Process >

After the acid treatment step, the β -type sialon powder is separated from the acid by a filter or the like, and the separated β -type sialon powder is washed with water. The washed β -type sialon powder was filtered with a filter to obtain phosphor powder containing Eu-activated β -type sialon phosphor particles as a main component.

The phosphor powder of the present embodiment can be enclosed in a package made of an aluminum laminated film. That is, the package contains the phosphor powder of the present embodiment in a dry state inside the package.

(light-emitting device)

The light-emitting device of the embodiment includes a light-emitting element and a wavelength conversion portion using the phosphor powder of the above-described embodiment. More specifically, the light emitting device is a white Light Emitting Diode (LED) including the phosphor powder of the present embodiment. In such an LED, it is preferable to use a phosphor powder encapsulated in an encapsulant. Such a sealing material is not particularly limited, and examples thereof include silicone resin, epoxy resin, perfluoropolymer resin, and glass. For applications requiring high output and high brightness, such as backlight applications of displays, a sealing material having durability even when exposed to high temperature and strong light is preferred, and from this viewpoint, a silicone resin is particularly preferred.

The light-emitting light source is preferably a light source that emits light of a wavelength of a color complementary to green emission of the β -type sialon phosphor or a light of a wavelength capable of efficiently exciting the β -type sialon phosphor, and for example, a blue light source (such as a blue LED) can be used. The peak wavelength of the light from the light-emitting source may preferably be in a range including blue (for example, in a range of 420nm to 560 nm), and more preferably may be in a range of 420nm to 480 nm.

The light-emitting device according to the embodiment may further include a phosphor (hereinafter referred to as "red phosphor") that emits red light having a peak wavelength of 610nm to 670nm when receiving excitation light having a wavelength of 455 nm. The red phosphor may be a single phosphor, or 2 or more phosphors. The light emitting device of the present invention having such a configuration can obtain white light by a combination of the β -type sialon phosphor emitting green light, the light emitting source generating blue light, and the red phosphor emitting red light, and can obtain light emission of various color ranges by changing the mixing ratio of these 3 colors. Especially if Mn activated K having a narrow half-value width of the luminescence spectrum is used₂SiF₆The phosphor is preferably a red phosphor because a light-emitting device with a high color gamut can be obtained.

The light emitting device of the present embodiment can improve luminance by using the phosphor powder as a wavelength conversion member.

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 by way of examples and comparative examples, but the present invention is not limited to these examples.

(example 1)

A method for producing the phosphor powder of example 1 will be described.

< mixing Process >

95.90% by mass of α -type silicon nitride powder (manufactured by Yushixing Co., Ltd., SN-E10 grade, oxygen content 1.0% by mass), 2.75% by mass of aluminum nitride powder (manufactured by Tokuyama Corporation, F grade, oxygen content 0.8% by mass), 0.56% by mass of alumina powder (manufactured by DAMIN chemical industry Co., Ltd., TM-DAR grade), and europium oxide powder (manufactured by shin-Etsu chemical industry Co., Ltd., TM-DAR grade) were mixed by a V-type mixer (S-3)RU grade, manufactured by kosha corporation) was mixed in an amount of 0.80 mass%, and the whole was passed through a sieve having a mesh size of 250 μm to remove aggregates, thereby obtaining a raw material mixed powder. The compounding ratio (first compounding composition (% by mass)) herein is designed such that: for the general formula of beta-sialon: si_6－zAl_zO_zN_8－zIn addition to the europium oxide, z is 0.22 as calculated from the Si/Al ratio.

< first firing Process >

200g of the raw material mixed powder having the first compounding composition obtained here was charged into a cylindrical boron nitride container (available from electrochemical Co., Ltd., N-1 grade) with a lid having an inner diameter of 10cm and a height of 10cm, and subjected to a heat treatment at 1850 ℃ for 4 hours in a pressurized nitrogen atmosphere of 0.8MPa in an electric furnace of a carbon heater (first firing step). The powder subjected to the heat treatment was passed through a sieve having a mesh opening of 45 μm. Note that the powder was entirely passed through the sieve. The mass ratio of the components is 70: a powder having passed through the sieve after the first firing step (referred to as a first fired powder) and a raw material mixed powder having the first formulation were mixed at a mixing ratio (second formulation (mass%)) of 30 by the same method as described above.

< second firing Process >

200g of the obtained mixed powder was charged in a cylindrical boron nitride container with a lid having an inner diameter of 10cm and a height of 10cm, and subjected to a heat treatment at 2020 ℃ for 12 hours in a pressurized nitrogen atmosphere of 0.8MPa in an electric furnace of a carbon heater (second firing step).

< crushing/pulverizing Process >

Since the heat-treated sample gradually became agglomerated, the agglomerated mass was coarsely pulverized with a hammer, and then pulverized with a supersonic jet pulverizer (Nippon Pneumatic mfg.co., ltd. system, PJM-80 SP). The pulverization conditions were such that the sample feed rate was 50 g/min and the pulverization air pressure was 0.3 MPa. The pulverized powder was passed through a sieve having a mesh opening of 45 μm. The sieve passage rate was 96%.

< annealing Process >

The second firing step was carried out by compacting 600g of the pulverized powder passed through a sieve having a mesh size of 45 μm and filling the compacted powder into a cylindrical boron nitride container having an inner diameter of 10cm and a height of 10cm and a lid. At this time, the powder is tightly filled to the extent of contact with the cap. The filled container was annealed at 1500 ℃ for 8 hours in an atmosphere of argon at atmospheric pressure in an electric furnace of a carbon heater. In the annealing temperature reduction, the temperature is reduced at 5 ℃/min in a temperature range of 1000 ℃ to 1500 ℃. The powder subjected to the annealing treatment was passed through a sieve having a mesh opening of 45 μm. The sieve passage was 95%.

< acid treatment Process >

The powder subjected to the annealing treatment was subjected to a reaction in a 1: 1 mixed acid, and soaking the mixture at 75 ℃ for 30 minutes.

< cleaning/filtration Process >

The powder after the acid treatment was precipitated, and the decantation for removing the supernatant liquid and the fine powder was repeated until the pH of the solution became 5 or more and the supernatant liquid became transparent, and the precipitate finally obtained was filtered and dried to obtain the phosphor powder of example 1. As a result of powder X-ray diffraction measurement, it was confirmed that the existing crystal phase was a β -type sialon single phase, and a β -type sialon phosphor was obtained as a single phase.

(example 2)

The second blending composition (mass%) of example 1 was changed so that the first pulverized powder and the raw material mixed powder having the first blending composition were 50: the phosphor powder of example 2 was produced in the same manner as in example 1 except that the mixing ratio was 50. The sieve passage when the annealed powder was passed through a sieve having a mesh opening of 45 μm was 95%.

(example 3)

The second blending composition (mass%) of example 1 was changed so that the first pulverized powder and the raw material mixed powder having the first blending composition were 30: 70, and the second firing was performed under the same conditions as in example 1. The pulverization conditions after the heat treatment were set such that the sample supply rate was 50 g/min and the pulverization air pressure was 0.5 MPa. Except for this, the phosphor powder of example 3 was produced in the same manner as in example 1. The sieve passage when the annealed powder was passed through a sieve having a mesh opening of 45 μm was 96%.

Comparative example 1

The phosphor powder of comparative example 1 was produced in the same manner as in example 1, except that the filling amount was 100g in the annealing step and filling was not performed reliably in accordance with the usual method for producing a β -type sialon phosphor. When the annealed powder was passed through a sieve having a mesh opening of 45 μm, the entire powder passed through the sieve.

Comparative example 2

The phosphor powder of comparative example 2 was produced in the same manner as in example 1, except that the temperature was lowered at 0.5 ℃/min in the temperature range of 1000 to 1500 ℃ during the annealing temperature lowering step. The sieve passage when the annealed powder was passed through a sieve having a mesh opening of 45 μm was 84%.

(evaluation of light-emitting characteristics of phosphor powder)

The phosphor powders of examples 1 to 3 and comparative examples 1 and 2 were evaluated for their emission characteristics as follows. The results are shown in Table 1.

The fluorescent characteristics of the phosphor powder were determined by measuring the fluorescence spectrum when irradiated with excitation light having a spectral wavelength of 455nm, and determining the peak intensity and peak wavelength, by filling the phosphor powder on a special solid sample holder by rhodamine B method and a spectrofluorometer calibrated by a standard light source (manufactured by Hitachi High-Technologies Corporation, F-7000). The peak intensity varies depending on the measurement apparatus and conditions, and therefore, the unit is arbitrary, and the phosphor powders of examples 1 to 3 and comparative examples 1 and 2 were continuously measured under the same conditions. The peak intensity of the phosphor powder of comparative example 1 was compared to 100%.

(evaluation of particle size distribution of phosphor powder)

The phosphor powders of examples 1 to 3 and comparative examples 1 and 2 were evaluated for particle size distribution under the following two conditions. The results are shown in Table 1.

< Condition 1: median diameter of pretreatment using ultrasonic homogenizer

30mg of the phosphor powder and 100ml of an aqueous solution of sodium hexametaphosphate adjusted to 0.2% were collected in a 200ml beaker, and then stirred uniformly at room temperature (25 ℃) with a spatula to such an extent that no precipitation occurs, thereby obtaining a dispersion.

The obtained dispersion was placed in a cylindrical container (inner diameter: 5.5cm) having a bottom surface of 2.75cm in radius, a cylindrical chip (outer diameter: 20mm) having a radius of 10mm and having an ultrasonic homogenizer (manufactured by Nippon Seiko Seisaku-Sho Co., Ltd., U.S. Pat. No. 150E) was immersed in the dispersion for 1.0cm or more, and ultrasonic waves were irradiated at a frequency of 19.5kHz and an output of 150W for 3 minutes to obtain a solution to be measured.

The measurement target solution was put into a dispersion medium filled in a circulation system using a flow cell type laser diffraction scattering particle size distribution measuring apparatus (MT 3300EXII, manufactured by Microtrac and Bel) to produce a measurement target sample, the measurement target sample was circulated, and the particle diameters of the phosphor powders were measured to obtain respective median diameters D₁₀、D₅₀、D₉₀。

< Condition 2: median diameter without pretreatment of ultrasonic homogenizer

The dispersion was prepared in the same manner as in the above condition 1, and the solution to be measured was obtained without the ultrasonic homogenizer treatment. The particle size of the phosphor powder was measured using a flow cell type laser diffraction scattering particle size distribution measuring apparatus in the same manner as in the above condition 1 for the obtained measurement target solution, and each median diameter D was obtained₁₀、D₅₀、D₉₀。

The evaluation results of the phosphor powders of examples 1 to 3 and comparative examples 1 and 2 are summarized in table 1 below. As a result, there was obtained a median diameter (D) of the pretreatment using the ultrasonic homogenizer₅₀) D2, the median diameter of the non-ultrasonic homogenizer pretreatment (D)₅₀) In other words, the median diameter measured without ultrasonic homogenizer treatment was D1, and D was calculated₅₀Ratio (D1/D2). From the values of D1/D2, it is understood that the degree of aggregation of the phosphor powder of comparative example 1 is lower than that of examples 1 to 3, and the result is almost monodisperse. In addition, it was found that in comparative example 2, the aggregation and disintegration were carried out by the ultrasonic homogenizer treatment, and the particles were mostly monodispersed, so that the amount of the polymer particles was larger than that in examples 1 to 3The phosphor powders are aggregated with each other.

[ Table 1]

(evaluation of light-emitting characteristics of LED Using beta-sialon phosphor)

The phosphor powder of example 1 and a fluoride phosphor, i.e., K, as a red phosphor were mixed₂SiF₆A phosphor (KR-3K 01, manufactured by Denko K.K.) was added to a silicone resin (JCR 6175, manufactured by Toray-Dow Corning corporation) and mixed by a rotation-revolution mixer (Awatori Kataro, manufactured by Thinky K.K.: ARV-310) to obtain a slurry. The slurry was potted in a surface mount type package to which a blue LED element having a peak wavelength of 450nm was bonded, and was further thermally cured to produce a white LED of example 4. The ratio of the amounts of the β -type sialon phosphor and the fluoride phosphor added was adjusted so that the chromaticity coordinates (x, y) of the white LED became (0.28, 0.27) during energization and light emission.

A white LED of example 5 was produced in the same manner as in example 4, except that the phosphor powder of example 2 was used instead of the phosphor powder of example 1. White LEDs of example 6 and comparative examples 3 and 4 were produced in the same manner as in example 4, except that the phosphor powders of example 3 and comparative examples 1 and 2 were used. The addition amount ratio of the β -type sialon phosphor to the fluoride phosphor was adjusted so that the chromaticity coordinates (x, y) of the white LED at the time of energization light emission became (0.28, 0.27).

(evaluation of Brightness)

The chromaticity when the white LEDs of examples 4 to 6 and comparative examples 3 and 4 were caused to emit light by passing light through a total beam measuring device (available from Otsuka Denshi Co., Ltd., a device obtained by combining a 300mm diameter integrating hemisphere with a spectrophotometer/MCPD-9800). 10 of the obtained white LEDs having chromaticity x of 0.275 to 0.284 and chromaticity y of 0.265 to 0.274 are selected, and the average value of the total light flux in the case of energization light emission is calculated. The evaluation result is a relative evaluation in which the average value of the total light flux of comparative example 3 is set to 100%. The results are shown in Table 2.

[ Table 2]

TABLE 2

	Total light beam
		Example 4	106
Example 5	106
		Example 6	105
Comparative example 3	100
		Comparative example 4	98

From the results of the examples and comparative examples shown in tables 1 to 2, it was confirmed that the phosphor powder of the present embodiment has a high luminance when used as a white LED, since the D1/D2 value is in a specific range, that is, in an appropriately aggregated state.

The present application claims priority based on Japanese application laid-open at 23/4/2019, Japanese application laid-open at 2019-No. 2019-081456, and the entire disclosure thereof is incorporated herein.