Phosphor powder, method for manufacturing phosphor powder, and light-emitting device

Abstract

One aspect of the present disclosure provides a phosphor powder that contains phosphor particles which have a main crystal phase that has the same crystal structure as CaAlSiN3, while being represented by general formula (Sr1-x-y, Cax, Euy)AlSi(N, O)3 (wherein x and y satisfy 0.0100 ≤ x ≤ 0.0300 and 0.0500 ≤ y ≤ 0.0900).

Description

[Technical Field]

[0001] The present disclosure relates to a phosphor powder, a method for manufacturing the phosphor powder, and a light-emitting device. [Background technology]

[0002] Light-emitting devices having light-emitting elements such as light-emitting diodes are used in general lighting, backlights for liquid crystal displays, LED displays, etc. LED displays use light-emitting elements that have, for example, a light-emitting element that emits blue light and a wavelength converter that absorbs the primary light from the light-emitting element and emits light of a different wavelength. Various phosphors, such as red phosphors and green phosphors, are used as the wavelength converter.

[0003] Known red phosphors include CASN-based phosphors such as CASN phosphor and SCASN phosphor (see, for example, Patent Document 1). These CASN-based phosphors are generally synthesized by heating raw material powders containing europium oxide or europium nitride, calcium nitride, silicon nitride, and aluminum nitride. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2005 / 052087 Summary of the Invention [Problem to be solved by the invention]

[0005] To obtain an LED display with high color reproducibility, it is important to use green and red phosphors that have emission peak wavelengths in their respective wavelength ranges and exhibit sufficient emission intensity. In a micro LED display, for example, a cured resin layer filled with green or red phosphors is placed on a blue LED, and multicoloring is achieved by wavelength conversion using blue primary light as excitation light. It is therefore necessary to achieve a wide color gamut for the cured resin layer.

[0006] Regarding red phosphors, as the emission spectrum of the phosphor shifts to the long wavelength region and the reddish color deepens, the overlap with the human luminosity curve decreases, and the brightness tends to be insufficient. In other words, with red phosphors, it is difficult to achieve both a reddish color to improve the color rendering properties of the light-emitting device using them and brightness.

[0007] The present disclosure aims to provide a phosphor powder capable of emitting fluorescence with a sufficient reddish hue while exhibiting excellent brightness, and a method for producing the same. The present disclosure also aims to provide a light-emitting device using the above-mentioned phosphor powder and capable of exhibiting excellent color rendering properties. [Means for solving the problem]

[0008] One aspect of the present disclosure is a crystalline alloy in which the predominant crystalline phase has the same crystalline structure as CaAlSiN3 and has the general formula: (Sr 1-x-y ,Ca x ,EU y )AlSi(N,O)3 [in the general formula, x and y satisfy 0.0100≦x≦0.0300 and 0.0500≦y≦0.0900].

[0009] The phosphor powder contains phosphor particles whose main crystal structure is the same as CaAlSiN3, and therefore can function as a red phosphor. Furthermore, the phosphor powder has an element ratio of strontium (Sr), calcium (Ca), and europium (Eu) within the above-mentioned range, enabling it to emit fluorescence with a sufficient reddish hue while exhibiting excellent brightness. While the reason for this effect is unclear, the inventors speculate as follows: First, in SCASN phosphors, as the calcium content in the composition formula decreases (i.e., as the proportion of calcium sites in the crystal lattice replaced by other elements increases), the half-width of the emission spectrum narrows and brightness improves, but the emission peak wavelength tends to shift toward shorter wavelengths and the reddish hue of the fluorescence tends to decrease. On the other hand, as the europium content in the composition formula of SCASN phosphors increases, concentration quenching occurs due to the increase in europium, resulting in a decrease in luminous efficiency, but the emission peak wavelength tends to shift toward longer wavelengths. Strontium, calcium, and europium are elements that share the same site in the crystal lattice, and in the above phosphor powder, the proportions of strontium, calcium, and europium in the composition formula are specific and satisfy the above-mentioned ranges of x and y. This is presumably to improve the luminance and adjust the wavelength position, thereby increasing the overlap with the human luminosity curve, while keeping the emission peak position in a sufficiently reddish wavelength range and improving the luminous intensity.

[0010] The phosphor powder may have an emission peak wavelength of 635 nm or longer when irradiated with light having a wavelength of 455 nm. When the emission peak wavelength is 635 nm or longer, the phosphor powder can be more suitably used as a red phosphor that emits fluorescence with a more excellent reddish hue.

[0011] One aspect of the present disclosure provides a light emitting device including a light emitting element that emits primary light and a wavelength converter that absorbs a portion of the primary light and emits secondary light having a wavelength longer than the wavelength of the primary light, wherein the wavelength converter includes the above-mentioned phosphor powder.

[0012] The light emitting device contains the above-mentioned phosphor powder, and therefore can exhibit excellent color rendering properties. Also, the light emitting device contains the above-mentioned phosphor powder, and therefore can be expected to exhibit sufficient brightness.

[0013] One aspect of the present disclosure provides a method for producing a phosphor powder, the method comprising: a firing step of heat-treating a mixed powder containing a raw material powder including a strontium source, a calcium source, an aluminum source, a silicon source, a nitrogen source, and a europium source, and a nucleating agent composed of a CASN-based compound, to obtain a fired product; and an annealing step of heat-treating the fired product at a temperature lower than the heat treatment temperature in the firing step to obtain an annealed product, wherein in the raw material powder, the ratio of the total amount of substance of strontium, calcium, and europium to the amount of substance of aluminum exceeds 1.0000, and the amount of substance of calcium is 0.0050 or more and the amount of substance of europium is 0.0880 or less, relative to the amount of substance of aluminum.

[0014] The phosphor powder manufacturing method described above involves adjusting the ratio of the total amount of strontium, calcium, and europium to the amount of aluminum in the raw material powder to exceed 1 and the amounts of calcium and europium to fall within a predetermined range. Furthermore, firing is performed in the presence of a nucleating agent to form desired particles, thereby enabling the preparation of a phosphor powder represented by the general formula described above. Conventionally, in the manufacture of CASN-based phosphors, raw materials are typically mixed according to the target composition, and the composition is adjusted so that the ratio of the total amount of strontium, calcium, and europium to the amount of aluminum is 1. For example, increasing the amount of calcium to cause the ratio to deviate from 1 can result in the formation of heterophases and a decrease in luminous efficiency. In contrast, it has been discovered that by adjusting the amounts of calcium and europium to fall within a predetermined range, the formation of the heterophases can be suppressed, and the phosphor described above can be manufactured using the manufacturing method described herein. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to provide a phosphor powder capable of emitting fluorescence with a sufficient reddish hue while exhibiting excellent brightness, and a method for manufacturing the same. Furthermore, according to the present disclosure, it is possible to provide a light-emitting device that uses the above-mentioned phosphor powder and exhibits excellent color rendering properties. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing the relationship between the luminosity curve and the emission spectrum of the SCASN phosphor. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

[0018] Unless otherwise specified, the materials exemplified in this specification can be used singly or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0019] One embodiment of the phosphor powder has a predominant crystalline phase having a crystalline structure identical to CaAlSiN3 and has the general formula: (Sr 1-x-y ,Ca x ,EU y )AlSi(N,O)3 [wherein x and y satisfy 0.0100≦x≦0.0300 and 0.0500≦y≦0.0900]. 1-x-y ,Ca x ,EU yIn AlSi(N,O)3, the value of x may be, for example, 0.0105 or more, 0.0108 or more, 0.0110 or more, or 0.117 or more, and may be 0.0280 or less, 0.0250 or less, or 0.0240 or less. The value of y may be, for example, 0.0600 or more, 0.0700 or more, or 0.0750 or more, and may be 0.0880 or less, or 0.0850 or less. The phosphor powder is an aggregate of phosphor particles. The phosphor particles may be a CASN phosphor or a SCASN phosphor.

[0020] The crystalline structure of phosphor particles can be confirmed by powder X-ray diffraction. The contents of strontium (Sr), calcium (Ca), europium (Eu), aluminum (Al), and silicon (Si) in the composition of phosphor particles can be determined by preparing a sample solution by pressure acid decomposition of the measurement target and then quantitatively analyzing the solution using an ICP optical emission spectrometer.

[0021] The lower limit of the emission peak wavelength of the phosphor powder may be, for example, 635 nm or more, 636 nm or more, 637 nm or more, more than 637 nm, or 638 nm or more. When the lower limit of the emission peak wavelength is within the above range, the phosphor powder can be more suitably used as a red phosphor that tends to emit a more reddish color. The upper limit of the emission peak wavelength of the phosphor powder may be, for example, 645 nm or less, 642 nm or less, 640 nm or less, less than 640 nm, or 639 nm or less. When the upper limit of the emission peak wavelength is within the above range, the overlap between the emission spectrum of the phosphor powder and the human luminosity curve can be further increased, and the phosphor powder can be more suitably used as a red phosphor with excellent brightness. The emission peak wavelength of the phosphor powder may be adjusted within the above range, for example, 635 to 645 nm.

[0022] The half-width at the emission peak wavelength of the phosphor powder is relatively small. The upper limit of the half-width at the emission peak wavelength of the phosphor powder may be, for example, 75.0 nm or less, 74.8 nm or less, 74.6 nm or less, 74.5 nm or less, 74.4 nm or less, less than 74.4 nm, or 74.3 nm or less. When the upper limit of the half-width is within the above range, the luminance of the phosphor powder can be further improved. The lower limit of the half-width at the emission peak wavelength of the phosphor powder may be, for example, 70.0 nm or more, 71.0 nm or more, 72.0 nm or more, 73.0 nm or more, or 73.5 nm or more. When the lower limit of the half-width is within the above range, emission with a more excellent reddish hue can be achieved. The half-width at the emission peak wavelength of the phosphor powder may be within the above range, for example, 70.0 to 75.0 nm, or 73.5 to 74.3 nm.

[0023] In this specification, the emission peak wavelength of a phosphor refers to a value determined by measuring the fluorescence spectrum when irradiated with light having a wavelength of 455 nm. In this specification, the half-width refers to the full width at half maximum (FWHM) and can be determined from the fluorescence spectrum obtained by measuring the fluorescence spectrum when irradiated with light having a wavelength of 455 nm.

[0024] The upper limit of the average particle size of the phosphor powder may be, for example, 40.0 μm or less, 30.0 μm or less, or 25.0 μm or less. By setting the upper limit of the average particle size within the above range, it is possible to suppress variations in the chromaticity of the emitted color when the phosphor powder is used on the light-emitting surface of an LED. The lower limit of the average particle size of the phosphor powder may be, for example, 0.1 μm or more, 0.5 μm or more, or 1.0 μm or more. By setting the lower limit of the average particle size within the above range, it is possible to further suppress a decrease in brightness. The average particle size of the phosphor powder may be adjusted within the above range, and can be, for example, 0.1 to 40.0 μm, 0.5 to 30.0 μm, or 1.0 to 25.0 μm.

[0025] In this specification, the average particle size refers to the particle size (D50, median diameter) at which the cumulative value from the smallest particle size reaches 50% of the total in the volume-based particle size distribution curve measured by laser diffraction / scattering. The particle size distribution curve for phosphor powder is measured in accordance with the particle size distribution measurement method by laser diffraction / scattering described in JIS R 1629:1997, "Method for Measuring Particle Size Distribution of Fine Ceramics Raw Materials by Laser Diffraction / Scattering." A particle size distribution analyzer can be used for the measurement. Specifically, 0.1 g of the phosphor powder to be measured is first placed in 100 mL of ion-exchanged water, a small amount of sodium hexametaphosphate is added, and the sample is dispersed using an ultrasonic homogenizer for 3 minutes. The particle size is measured using a particle size distribution analyzer, and the D50 is determined from the resulting particle size distribution. D50 is also referred to as the median diameter. An example of a particle size distribution analyzer that can be used is the "Microtrac MT3300EX II" (product name) manufactured by Microtrac Bell Corporation. As the ultrasonic homogenizer, for example, "Ultrasonic Homogenizer US-150E" (product name, tip size: φ20, Amplitude: 100%, oscillation frequency: 19.5 KHz, amplitude: approximately 31 μm) manufactured by Nippon Seiki Seisakusho Co., Ltd. can be used.

[0026] The above-mentioned phosphor powder can emit fluorescence with a sufficient reddish hue while exhibiting excellent brightness, and can therefore be suitably used as a phosphor for light-emitting devices such as LEDs, display devices, etc. The light-emitting devices, etc. obtained in this manner can exhibit excellent color rendering properties and sufficient brightness.

[0027] The above-mentioned phosphor powder can be produced, for example, by the following method: One embodiment of the method for producing a phosphor powder includes a firing step of heat-treating a mixed powder containing a raw material powder including a strontium source, a calcium source, an aluminum source, a silicon source, a nitrogen source, and a europium source, and a nucleating agent composed of a CASN-based compound, to obtain a fired product, and an annealing step of heat-treating the fired product at a temperature lower than the heat treatment temperature in the firing step to obtain an annealed product.

[0028] The terms "strontium source," "calcium source," "aluminum source," "silicon source," "nitrogen source," and "europium source" refer to compounds or elements that serve as sources of strontium (Sr), calcium (Ca), aluminum (Al), silicon (Si), nitrogen (N), and europium (Eu), respectively. Note that when strontium nitride, for example, is used as the strontium source, the strontium nitride is both a strontium source and a nitrogen source.

[0029] Examples of strontium compounds include strontium nitride (Sr3N2), strontium oxide (SrO), and strontium hydroxide (Sr(OH)2).

[0030] Examples of calcium compounds include calcium nitride (Ca3N2), calcium oxide (CaO), and calcium hydroxide (Ca(OH)2).

[0031] Examples of aluminum compounds include aluminum nitride (AlN), aluminum oxide (Al2O3), and aluminum hydroxide (Al(OH)3).

[0032] Examples of silicon compounds include silicon nitride (Si3N4) and silicon oxide (SiO2). It is preferable to use silicon nitride with a high α fraction. The α fraction of silicon nitride may be, for example, 80 mass% or more, 90 mass% or more, or 95 mass% or more. When the α fraction of silicon nitride is within the above range, the growth of primary particles of the inorganic compound can be promoted.

[0033] The europium source refers to a compound or element that serves as a supply source of europium. The compound having europium as a constituent element (europium compound) may be, for example, any one of a nitride, an oxide, an oxynitride, and a hydroxide, but is preferably an oxide.

[0034] Examples of europium compounds include europium oxide (europium oxide), europium nitride (europium nitride), and europium halides. Examples of europium halides include europium fluoride, europium chloride, europium bromide, and europium iodide. The europium compound preferably includes europium oxide. The valence of europium in the europium compound may be divalent or trivalent, and is preferably divalent.

[0035] In the raw material powder, the ratio of the total amount of strontium, calcium, and europium to the amount of aluminum exceeds 1.0000, and the amount of calcium is 0.0050 or more and the amount of europium is 0.0880 or less, based on the amount of aluminum.

[0036] In the raw material powder, the lower limit of the ratio of the total amount of strontium, calcium, and europium to the amount of aluminum may be, for example, 1.0200 or more, 1.0300 or more, 1.0400 or more, 1.0450 or more, or 1.0500 or more. By setting the lower limit of this ratio within the above range, the reddishness and brightness of the fluorescence spectrum emitted by the obtained phosphor powder can be both achieved at a higher level. In the raw material powder, the upper limit of the ratio of the total amount of strontium, calcium, and europium to the amount of aluminum may be, for example, 1.5000 or less, 1.4000 or less, 1.3000 or less, 1.2000 or less, or 1.1000 or less. By setting the upper limit of this ratio within the above range, the formation of heterophases can be more sufficiently suppressed. In the raw material powder, the ratio of the total amount of strontium, calcium, and europium to the amount of aluminum may be adjusted within the above range, for example, more than 1.0000 and not more than 1.5000, more than 1.0000 and not more than 1.3000, or 1.0200 to 1.2000.

[0037] The lower limit of the amount of substance of calcium in the raw material powder may be, for example, 0.0050 or more, 0.0100 or more, 0.0105 or more, 0.0108 or more, 0.0110 or more, 0.0130 or more, or 0.0150 or more, based on the amount of substance of aluminum. When the lower limit of the amount of substance of calcium is within the above range, light emission with a more excellent reddish hue can be achieved. The upper limit of the amount of substance of calcium in the raw material powder may be, for example, 0.0280 or less, 0.0250 or less, 0.0240 or less, or 0.0220 or less, based on the amount of substance of aluminum. When the upper limit of the amount of substance of calcium is within the above range, light emission brightness can be further improved. The amount of substance of calcium in the raw material powder may be adjusted within the above range, and may be, for example, 0.0050 to 0.0280, based on the amount of substance of aluminum.

[0038] The lower limit of the amount of substance of europium in the raw material powder may be, for example, 0.0550 or more, 0.0600 or more, 0.0650 or more, or 0.0700 or more, based on the amount of substance of aluminum. When the lower limit of the amount of substance of europium is within the above range, light emission with a more excellent reddish hue can be achieved. The upper limit of the amount of substance of europium in the raw material powder may be, for example, 0.0880 or less, 0.0860 or less, 0.0850 or less, or 0.0830 or less, based on the amount of substance of aluminum. When the upper limit of the amount of substance of europium is within the above range, light emission brightness can be further improved. The amount of substance of europium in the raw material powder may be adjusted within the above range, and may be, for example, 0.0550 to 0.0880, based on the amount of substance of aluminum.

[0039] The nucleating agent made of a CASN-based compound blended into the mixed powder may have the same crystal structure as CaAlSiN3, and may contain a luminescent center element.

[0040] The firing in the firing step may be carried out, for example, by filling a heat-resistant container with a lid with the mixed powder to be fired and heating the container. Examples of materials that can be used to form the heat-resistant container include boron nitride, tungsten, molybdenum, and tantalum. An electric furnace or the like can be used for heating.

[0041] The firing process is carried out by adjusting conditions such as firing temperature, firing time, firing pressure, and firing atmosphere in order to form the same crystal structure as CaAlSiN3 and reduce variations in composition when forming the crystal structure.

[0042] It is desirable that the firing temperature in the firing step be constant throughout the process. The firing temperature in the firing step may be, for example, 1500°C or higher, or 1550°C or higher. By setting the lower limit of the firing temperature within the above range, variation in the composition of the resulting fired product can be further reduced. The firing temperature in the firing step may be, for example, 2000°C or lower, 1980°C or lower, or 1950°C or lower. By setting the upper limit of the firing temperature within the above range, volatilization of various compounds that serve as raw materials for the inorganic compound can be suppressed, and decomposition of the formed inorganic compound can be suppressed, thereby suppressing destruction of the crystalline structure. The firing temperature in the firing step can be adjusted within the above range, and may be, for example, 1500 to 2000°C or 1550 to 1950°C.

[0043] The lower limit of the firing time in the firing step may be, for example, 0.5 hours or more, 1.0 hours or more, 1.5 hours or more, 3.0 hours or more, or 4.0 hours or more. By setting the lower limit of the firing time within the above range, it is possible to further promote the conversion of the various raw material compounds into a fired product having the same crystal structure as the CaAlSiN3 crystal phase, thereby improving the yield in the production of phosphor powder. The upper limit of the firing time in the firing step may be, for example, 30.0 hours or less, 20.0 hours or less, 10.0 hours or less, or 8.0 hours or less. By setting the upper limit of the firing time within the above range, it is possible to further suppress excessive crystal growth of primary particles in the fired product. The firing time in the firing step can be adjusted within the above range, for example, 0.5 to 30.0 hours, 1.5 to 10.0 hours, or 4.0 to 8.0 hours.

[0044] In this specification, the firing time means the time (retention time) during which the temperature of the environment surrounding the object to be heated is maintained at a predetermined temperature after the temperature reaches that temperature.

[0045] The firing step may be carried out under atmospheric pressure or under pressure. When the firing step is carried out under a pressurized environment, the lower limit of the firing pressure in the firing step may be, for example, 0.1 MPaG or more, or 0.2 MPaG or more. When the lower limit of the firing pressure is within the above range, decomposition of the main crystals constituting the fired product can be further suppressed. The upper limit of the firing pressure in the firing step may be, for example, 1.0 MPaG or less, or 0.9 MPaG or less. When the upper limit of the firing pressure is within the above range, decomposition of the inorganic compound can be further suppressed. The pressure in the firing step can be adjusted within the above range, and may be, for example, 0.1 to 1.0 MPaG, or 0.1 to 0.9 MPaG.

[0046] In this specification, pressure means gauge pressure.

[0047] The firing step is preferably carried out in an atmosphere containing at least one selected from the group consisting of a rare gas and an inert gas. The rare gas may contain, for example, argon, helium, or the like, or may contain or consist of argon. The inert gas may contain, for example, nitrogen, or the like, or may consist of nitrogen.

[0048] In the annealing step, the fired product is heat-treated at a temperature lower than the heat treatment temperature in the firing step to obtain an annealed product.

[0049] The temperature of the heat treatment in the annealing step may be, for example, 1200°C or higher, 1250°C or higher, or 1300°C or higher. When the lower limit of the heat treatment temperature is within the above range, crystal defects generated in the firing step and pulverization step can be reduced, and a phosphor powder with higher luminous efficiency can be obtained. The temperature of the heat treatment in the annealing step may be, for example, 1450°C or lower, 1400°C or lower, or 1350°C or lower. When the upper limit of the heat treatment temperature is within the above range, crystal defects can be sufficiently reduced while further suppressing decomposition of the main phase. The temperature of the heat treatment in the annealing step can be adjusted within the above range and may be, for example, 1200 to 1450°C, or 1250 to 1350°C.

[0050] The lower limit of the heat treatment time in the annealing step may be, for example, 0.5 hours or more, 1.0 hours or more, 1.5 hours or more, 3.0 hours or more, or 4.0 hours or more. The upper limit of the heat treatment time in the annealing step may be, for example, 30.0 hours or less, 20.0 hours or less, 10.0 hours or less, 8.0 hours or less, or 5.0 hours or less. The heat treatment time in the annealing step can be adjusted within the above-mentioned range and may be, for example, 0.5 to 30.0 hours, 1.5 to 10.0 hours, or 4.0 to 8.0 hours.

[0051] The annealing step may be performed under atmospheric pressure or under pressure. When the annealing step is performed under a pressurized environment, the lower limit of the pressure in the annealing step may be, for example, 0.1 MPaG or more, or 0.2 MPaG or more. When the lower limit of the pressure is within the above range, decomposition of the phosphor particles can be further suppressed. The upper limit of the pressure in the annealing step may be, for example, 1.0 MPaG or less, or 0.9 MPaG or less. When the upper limit of the pressure is within the above range, decomposition of the formed phosphor particles can be further suppressed. The pressure in the annealing step can be adjusted within the above range, and may be, for example, 0.1 to 1.0 MPaG, or 0.1 to 0.9 MPaG.

[0052] The annealing step is preferably performed in an atmosphere containing at least one selected from the group consisting of a rare gas and an inert gas. The rare gas may contain, for example, argon, helium, or the like, or may contain or consist of argon. The inert gas may contain, for example, nitrogen, or the like, or may consist of nitrogen.

[0053] The above-described method for producing a phosphor powder may include other steps in addition to the firing step and the annealing step, such as a crushing step, a classification step, and an acid treatment step.

[0054] The crushing process is a process for crushing the fired product obtained in the firing process or the annealed product obtained in the annealing process, which may be in the form of lumps, to adjust the particle size. In the crushing process, a mortar or a mortar may be used, or a general crusher or crusher may be used. Examples of crushers and crushers include a ball mill, a jet mill, and a Henschel mixer. While the fired product in the form of lumps may be crushed using a relatively high-intensity method, when crushing the annealed product in the form of lumps, it is desirable to crush the lumps under gentle conditions in order to prevent scratches, cracks, etc. on the surface of the phosphor particles. To achieve gentle crushing, for example, the crushing process is desirably performed using a wet ball mill in the presence of a medium such as ion-exchanged water. Furthermore, zirconia balls can be used in the ball mill.

[0055] The classification step may be a step of removing fine particles that reduce the luminance and other properties of the phosphor powder. When the required level of optical properties of the phosphor powder is high, the above-mentioned method for producing a phosphor powder desirably includes a classification step. The classification step may be, for example, a decantation method. The classification step is performed by putting the material to be treated (e.g., phosphor powder that has been subjected to a crushing step) into a dispersion medium, preparing and stirring a dispersion, allowing the phosphor powder in the dispersion to settle, and removing the supernatant. After removing the supernatant, the precipitate is collected by filtration and dried to obtain a phosphor powder from which the fine particles have been removed. In the classification step, the preparation of the dispersion and the removal of the supernatant may be repeated. Examples of dispersion media include an aqueous solution of sodium hexametaphosphate.

[0056] The acid treatment step may be a step of treating the phosphor powder with an acid to reduce the content of impurities that do not contribute to light emission. Examples of acids include hydrofluoric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid. The acid may include at least one selected from the group consisting of hydrofluoric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid, and may be a mixed acid, but is preferably hydrochloric acid. The acid treatment step is carried out by bringing the phosphor powder into contact with the acid. Specifically, the phosphor powder is placed in an aqueous solution containing the acid to prepare a dispersion, and the dispersion is treated for a predetermined period of time while being stirred.

[0057] The lower limit of the stirring time in the acid treatment step may be, for example, 0.1 hour or more, 0.5 hour or more, or 1.0 hour or more. The upper limit of the stirring time may be, for example, 6.0 hours or less, 3.0 hours or less, or 1.5 hours or less. Furthermore, in the acid treatment step, the aqueous solution may be subjected to the acid treatment in a cooled, heated, or boiled state, and the temperature of the aqueous solution may be, for example, 20 to 90°C, or 30 to 80°C. After the acid treatment, the phosphor powder may be washed with water to remove the acid, and then dried. The drying temperature may be, for example, 100 to 120°C. The drying time may be, for example, about 12 hours.

[0058] The above-mentioned phosphor powder is suitable as a phosphor to be used in a light-emitting device such as a display device. One embodiment of the light-emitting device is a light-emitting device including a light-emitting element that emits primary light, and a wavelength converter that absorbs a part of the primary light and emits secondary light having a wavelength longer than the wavelength of the primary light.

[0059] The light emitting element that emits the primary light may be, for example, an InGaN blue LED.

[0060] The wavelength converter includes the above-mentioned phosphor powder. The wavelength converter may include other phosphors in addition to the above-mentioned phosphor powder. Examples of the other phosphors include red phosphors, yellow phosphors, yellow-green phosphors, and green phosphors other than the above-mentioned phosphor powders. The other phosphors can be selected depending on the application of the phosphor composition, and can be selected and combined depending on, for example, the brightness, color, and color rendering properties required for the light-emitting device. Examples of red phosphors include conventional CASN-based phosphors. Examples of green to yellow phosphors (phosphors having a fluorescent wavelength in the green to yellow wavelength band) include YAG phosphors and LuAG phosphors. Examples of yellow phosphors include Ca-α-SiAlON phosphors, and examples of green phosphors include β-SiAlON phosphors.

[0061] The light-emitting element and the wavelength converter may be dispersed in a sealing resin or the like. The sealing resin is preferably colorless and has excellent transparency to visible light wavelengths. The sealing resin may generally be one that is recognized as transparent. The resin may be, for example, a silicone resin or an acrylic resin.

[0062] Display devices such as monitors are required to provide sufficient brightness for the transmission of information. To achieve this, it is desirable that the light components emitted from the display fall within a range where the human luminous efficiency is high. The luminous efficiency is generally determined based on the standard luminous efficiency curve established by the International Commission on Illumination (CIE). The more the light's emission spectrum overlaps with this standard luminous efficiency curve, the brighter it will appear to humans. The standard luminous efficiency curve is a curve close to a normal distribution, peaking around 550 nm and extending from 400 to 700 nm. For example, in bright places, humans are said to perceive light around 555 nm as most intense.

[0063] As shown in FIG. 1, the emission spectrum of SCASN phosphors generally overlaps with the standard luminous efficacy curve, making them useful as red phosphors. The emission spectrum of SCASN phosphors generally spans 600 to 800 nm. The phosphor powder described above has a specific composition in which the proportions of strontium, calcium, and europium in the composition formula satisfy the above-mentioned ranges of x and y. This shifts the peak position of the emission spectrum toward shorter wavelengths, resulting in a greater overlap with the standard luminous efficacy curve and sufficient brightness. Furthermore, since the phosphor powder exhibits a sufficient reddish tint, it can be a useful red phosphor for producing display devices with excellent brightness.

[0064] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. Furthermore, the descriptions of the above embodiments can be applied to each other. [Example]

[0065] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0066] Example 1 [Preparation of nucleating agent] First, 60.61 g of α-type silicon nitride (Si3N4, manufactured by Ube Industries, Ltd., SN-E10 grade), 53.13 g of aluminum nitride (AlN, manufactured by Tokuyama Corporation, E grade), and 13.68 g of europium oxide (Eu2O3, manufactured by Shin-Etsu Chemical Co., Ltd.) were placed in a container and premixed.

[0067] Next, in a glove box maintained in a nitrogen atmosphere with a moisture content of 1 mass ppm or less and an oxygen concentration of 50 ppm or less, 5.76 g of calcium nitride (CaN, manufactured by Materion) and 106.82 g of strontium nitride (SrN, manufactured by Kojundo Chemical Laboratory Co., Ltd., purity 2N) were further placed in the container and dry-mixed to obtain a mixture.

[0068] In a glove box, 240 g of the mixture was placed in a tungsten container with a lid. After closing the lid, the container was removed from the glove box and placed in an electric furnace equipped with a carbon heater. The electric furnace was then evacuated to a vacuum until the pressure inside was 0.1 PaG or less.

[0069] While continuing to evacuate, the temperature inside the electric furnace was raised to 600°C. After reaching 600°C, nitrogen gas was introduced into the electric furnace and the pressure inside the electric furnace was adjusted to 0.9 MPaG. Then, in a nitrogen gas atmosphere, the temperature inside the electric furnace was raised to 1950°C, and after reaching 1950°C, heat treatment was carried out for 8 hours. Then, heating was stopped and the mixture was cooled to room temperature. After cooling to room temperature, red lumps were recovered from the container. The recovered lumps were crushed in a mortar and sieved to prepare core particles (nucleating agent) with an average particle size of 16 μm.

[0070] [Manufacturing phosphor powder] 51.50 g of α-type silicon nitride (Si3N4, manufactured by Ube Industries, Ltd., SN-E10 grade), 45.14 g of aluminum nitride (AlN, manufactured by Tokuyama Corporation, E grade), 15.50 g of europium oxide (Eu2O3, manufactured by Shin-Etsu Chemical Co., Ltd.), and 24.00 g of the nucleating agent prepared as described above were weighed and premixed in a container.

[0071] Next, in a glove box maintained in a nitrogen atmosphere with a moisture content of 1 mass ppm or less and an oxygen concentration of 50 ppm or less, 0.27 g of calcium nitride (Ca3N2, manufactured by Materion) and 103.58 g of strontium nitride (Sr3N2, manufactured by Kojundo Chemical Laboratory Co., Ltd., purity 2N) were weighed into the container and dry-mixed. This resulted in a mixed powder. The relationship between the amounts of the nucleating agent and the raw material powder (mass %) and the breakdown of the amounts of each element in the raw material powder (molar ratio) are shown in Table 1.

[0072] In a glove box, 240 g of the mixed powder was placed in a tungsten container with a lid. After closing the lid, the container was removed from the glove box and placed in an electric furnace equipped with a carbon heater. The electric furnace was then evacuated to a vacuum until the pressure inside was 0.1 PaG or less.

[0073] While continuing to evacuate, the temperature inside the electric furnace was raised to 600°C. After reaching 600°C, nitrogen gas was introduced into the electric furnace and the pressure inside the electric furnace was adjusted to 0.9 MPaG. The temperature inside the electric furnace was then raised to 1950°C in a nitrogen gas atmosphere, and after reaching 1950°C, heat treatment was carried out for 8 hours. Heating was then terminated and the material was allowed to cool to room temperature. After cooling to room temperature, red lumps were recovered from the container. The recovered lumps were crushed and sieved to adjust the particle size, and a fired powder was obtained.

[0074] The resulting sintered powder was loaded into a tungsten container and quickly transferred to an electric furnace equipped with a carbon heater. The furnace was thoroughly evacuated until the pressure inside the furnace reached 0.1 PaG or less. Heating was started while continuing the evacuation. When the temperature reached 600°C, argon gas was introduced into the furnace and the pressure inside the furnace was adjusted to atmospheric pressure. After the introduction of argon gas began, the temperature continued to rise to 1350°C. After the temperature reached 1350°C, the heat treatment was carried out for 8 hours. Then, heating was stopped and the mixture was cooled to room temperature. After cooling to room temperature, the annealed powder was recovered from the container. The recovered powder was passed through a sieve to adjust the particle size. In this way, the annealed powder was obtained.

[0075] The annealed powder was placed in 2.0 M hydrochloric acid at room temperature to a slurry concentration of 25% by mass and immersed for 1 hour. This resulted in an acid treatment. After the acid treatment, the hydrochloric acid slurry was boiled for 1 hour while stirring. The boiled slurry was cooled to room temperature and filtered to separate the acid treatment liquid from the solid content, yielding an acid-treated product. The acid-treated product was then dried in a dryer set at a temperature between 100 and 120°C for 12 hours, yielding an acid-treated powder.

[0076] The acid-treated powder was placed in an alumina crucible, and the temperature was increased at a rate of 10° C. / min in the atmosphere, followed by heat treatment at 400° C. for 3 hours. After the heat treatment, the mixture was allowed to cool to room temperature, yielding a heat-treated powder.

[0077] The obtained heat-treated powder was subjected to powder X-ray diffraction using CuKα radiation using an X-ray diffractometer (Rigaku Corporation, product name: Ultima IV). The obtained X-ray diffraction pattern was identical to that of CaAlSiN3 crystals, confirming that the main crystalline phase had the same crystal structure as CaAlSiN3 crystals. This heat-treated powder was used as the phosphor powder of Example 1.

[0078] (Example 2, Comparative Examples 1 to 4) A phosphor powder was prepared in the same manner as in Example 1, except that the mixing ratio was adjusted so that the breakdown (molar ratio) of the amount of each element in the raw material powder was as shown in Table 1.

[0079] [Table 1]

[0080] <Evaluation of phosphor powder> The composition ratio, fluorescence emission peak wavelength and half width, color rendering index, and total luminous flux of each of the phosphor powders obtained in Examples 1 and 2 and Comparative Examples 1 to 4 were measured according to the methods described below. The results are shown in Table 2.

[0081] [Composition ratio] The phosphor powder was subjected to pressure acid decomposition to prepare a sample solution, which was then quantitatively analyzed using an ICP optical emission spectrometer to determine the composition ratio of the elements that make up the phosphor powder.

[0082] [Fluorescence emission peak wavelength and half-width] The fluorescence spectrum of the phosphor powder was measured using a spectrofluorometer (Hitachi High-Technologies Corporation, product name: F-7000) corrected using rhodamine B and a secondary standard light source. A solid sample holder attached to the spectrometer was used for the measurement, and the fluorescence spectrum was measured at an excitation wavelength of 455 nm. From the obtained fluorescence spectrum, the peak wavelength and half-width of the emission spectrum were determined.

[0083] [Color rendering index and total luminous flux] The color rendering properties and total luminous flux of the phosphor powder were evaluated by blending it with LuAG phosphor in silicone resin to prepare a white LED, which was used as an evaluation sample.

[0084] First, phosphor powder and LuAG yellow phosphor (with a peak emission wavelength of 535 nm when excited by 455 nm wavelength light) were blended with silicone resin, followed by degassing and kneading to obtain a kneaded mixture. The resulting kneaded mixture was potted into a surface-mount package to which a blue LED element with a peak wavelength of 450 nm was bonded, and then thermally cured to prepare a white LED. The blending ratio of phosphor powder to YAG phosphor was adjusted so that the chromaticity coordinates (x, y) of the white LED when energized were (0.460, 0.411).

[0085] The special color rendering index R9 and total luminous flux of the obtained white LED when it was energized and emitting light were measured using a total luminous flux measuring device (Otsuka Electronics Co., Ltd., a device combining a 500 mm diameter integrating hemisphere and a spectrophotometer (MCPD-9800)).

[0086] [Table 2] [Industrial Applicability]

[0087] According to the present disclosure, it is possible to provide a phosphor powder capable of emitting fluorescence with a sufficient reddish hue while exhibiting excellent brightness, and a method for manufacturing the same. Furthermore, according to the present disclosure, it is possible to provide a light-emitting device that uses the above-mentioned phosphor powder and exhibits excellent color rendering properties.

Claims

1. The main crystalline phase is CaAlSiN ３ It has the same crystal structure as General formula: (Sr １－ｘ－ｙ , Ca ｘ , Eu ｙ )AlSi(N,O) ３ A phosphor powder comprising phosphor particles represented by the general formula: [wherein x and y satisfy 0.0100≦x≦0.0300 and 0.0500≦y≦0.0900].

2. 2. The phosphor powder according to claim 1, which has an emission peak wavelength of 635 nm or more when irradiated with light having a wavelength of 455 nm.

3. A light emitting device comprising: a light emitting element that emits primary light; and a wavelength converter that absorbs a part of the primary light and emits secondary light having a wavelength longer than the wavelength of the primary light, A light emitting device, wherein the wavelength converter comprises the phosphor powder according to claim 1 .

4. A method for producing the phosphor powder according to claim 1 or 2, comprising: a firing step of heat-treating a mixed powder containing a raw material powder including a strontium source, a calcium source, an aluminum source, a silicon source, a nitrogen source, and a europium source, and a nucleating agent composed of a CASN-based compound, to obtain a fired product; an annealing step of heat-treating the fired product at a temperature lower than the heat treatment temperature in the firing step to obtain an annealed product; In the raw material powder, The ratio of the total amount of substance of strontium, calcium, and europium to the amount of substance of aluminum is greater than 1.0000, The amount of calcium is 0.0050 or more and the amount of europium is 0.0880 or less, based on the amount of aluminum. Method for manufacturing phosphor powder.

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