Alpha-sialon phosphor, light-emitting device, and method for producing alpha-sialon phosphor

Abstract

An Eu element-containing alpha-sialon phosphor in which the density of crystal defects is 1.0 * 1015 spins / g or less as the spin density of a signal in the vicinity of g = 2 detected by electron spin resonance measurement at 25 DEG C. Furthermore, the Eu-containing alpha-sialon phosphor has a crystal defect density of 1.0 * 1015 spins / g or less as a spin density of a signal in the vicinity of g = 2 detected by electron spin resonance measurement at 200 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to an α-sialon phosphor, a light emitting device, and a manufacturing method of an α-sialon phosphor. BACKGROUND

[0002] An α-sialon phosphor in which Eu and the like are activated is suitable for a wavelength conversion member of a white LED because it can efficiently convert blue light into long-wavelength light.

[0003] In an α-sialon phosphor, a part of Si-N bonds of an α-silicon nitride crystal is replaced with Al-N bonds and Al-O bonds, and in order to maintain electrical neutrality, a structure in which a specific element (Ca and Li, Mg, Y, or a lanthanoid metal other than La and Ce) intrudes into a crystal lattice and is solid-solved in the crystal lattice is formed. By setting a part of the element that is solid-solved as a rare earth element that becomes a light emitting center, a phosphor characteristic is exhibited. Among them, an α-sialon phosphor in which Ca is solid-solved and a part of it is substituted with Eu is relatively efficiently excited in a wide wavelength region from ultraviolet to blue and exhibits yellow or orange light emission.

[0004] Various attempts have been made to further improve the phosphor characteristic of an α-sialon phosphor (for example, Patent Documents 1 to 3 and the like).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-96882

[0008] Patent Document 2: Japanese Patent No. 6667025

[0009] Patent Document 3: Japanese Patent No. 6785333 SUMMARY

[0010] It is conceivable to apply a white LED using an α-sialon phosphor as a wavelength conversion member to an in-vehicle use.

[0011] In an in-vehicle use, it is required that various characteristics of a white LED do not change at a high temperature. However, as a result of preliminary research by the present inventors and the like, it was clarified that a white LED in which a conventional α-sialon phosphor is used as a wavelength conversion member greatly changes in light emission characteristics in a high-temperature environment.

[0012] The present application was completed in view of such a situation. One of the objects of the present application is to provide an α-sialon phosphor that is less likely to change in light emission characteristics even in a high-temperature environment when used as a wavelength conversion member of a white LED.

[0013] The present inventors have completed the invention provided below, which solves the above problems.

[0014] 1. An α-type sialon phosphor containing an Eu element, wherein,

[0015] the density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

[0016] 2. An α-type sialon phosphor containing an Eu element, wherein,

[0017] the density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

[0018] 3. The α-type sialon phosphor according to 2., wherein,

[0019] the density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

[0020] 4. The α-type sialon phosphor according to any one of 1. to 3., wherein,

[0021] the density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

[0022] 5. The α-type sialon phosphor according to any one of 1. to 4., wherein,

[0023] the density of crystal defects in the α-type sialon phosphor is 9.5 x 10 15 spins / g or less.

[0024] 6. The α-type sialon phosphor according to any one of 1. to 5.,

[0025] which has an internal quantum efficiency of 87% or more at 200°C.

[0026] 7. The α-type sialon phosphor according to any one of 1. to 6.,

[0027] The internal quantum efficiency thereof at 300°C is 80% or more.

[0028] 8. The α-sialon phosphor according to any one of 1. to 7., wherein

[0029] The internal quantum efficiency retention rate represented by {(internal quantum efficiency at 24°C) / (internal quantum efficiency at 300°C)} x 100[%] is 89% or more.

[0030] 9. The α-sialon phosphor according to any one of 1. to 8., wherein

[0031] The external quantum efficiency retention rate represented by {(external quantum efficiency at 24°C) / (external quantum efficiency at 300°C)} x 100[%] is 88% or more.

[0032] 10. The α-sialon phosphor according to any one of 1. to 9., wherein

[0033] The composition is represented by a general formula: (M1 x , M2 y , Eu z )(Si 12-(m+n) Al m+n )(O n N 16-n )

[0034] In the general formula,

[0035] M1 is a 1-valent Li element,

[0036] M2 is one or more 2-valent elements selected from the group consisting of Mg, Ca, and lanthanoid elements other than La and Ce,

[0037] 0≤x<2.0、0≤y<2.0、0<z≤0.5、0<x+y、0.3≤x+y+z≤2.0、0<m≤4.0、0<n≤3.0。

[0038] 11. A light-emitting device comprising:

[0039] a light-emitting element; and

[0040] a wavelength conversion section including the α-sialon phosphor according to any one of 1. to 10., and wavelength-converts light emitted from the light-emitting element.

[0041] 12. A method for producing an α-sialon phosphor, comprising the following steps:

[0042] a firing step in which a bulk α-sialon phosphor containing an Eu element is obtained by firing;

[0043] The pulverization process involves pulverizing the blocky α-type silon phosphor to obtain powdered α-type silon phosphor.

[0044] The N2 annealing process involves annealing the powdered α-type silon phosphor in a nitrogen atmosphere at a temperature range of 1200°C to 1700°C and for a time range of 5 to 30 hours.

[0045] The H2 annealing process involves annealing the powdered α-type silane phosphor in a hydrogen atmosphere at a temperature range of 1200°C to 1700°C and for a time range of 5 to 30 hours.

[0046] The acid treatment process involves applying an acidic aqueous solution to the powdered α-type silon phosphor after the H2 annealing process.

[0047] The luminescent properties of white LEDs using the α-type silron phosphor of the present invention as wavelength conversion components do not easily change even at high temperatures. Attached Figure Description

[0048] Figure 1 This is a schematic cross-sectional view showing an example of the structure of a light-emitting device. Detailed Implementation

[0049] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0050] In the accompanying drawings, the same reference numerals are used to denote the same constituent elements, and descriptions are omitted where appropriate.

[0051] To avoid complications, when multiple identical constituent elements exist in the same attached figure, sometimes only one of them is labeled, instead of all of them.

[0052] The accompanying drawings are for illustrative purposes only. The shapes or dimensions of the parts in the drawings may not necessarily correspond to actual objects.

[0053] In this specification, the expressions "X~Y" in the description of numerical ranges, unless otherwise specified, mean above X and below Y. For example, "1~5% by mass" means "more than 1% by mass and less than 5% by mass".

[0054] In this specification, "α-type silon phosphor containing Eu" is sometimes abbreviated as "α-type silon phosphor".

[0055] In this specification, "signal near g=2" literally means a signal with a g value near 2 in electron spin resonance measurements. Specifically, near g=2 means g=2±0.02.

[0056] <α-type sialon phosphor>

[0057] The α-type sialon phosphor of the present embodiment contains an Eu element. In another way of saying, the α-type sialon phosphor of the present embodiment is an Eu-activated α-type sialon phosphor.

[0058] The α-type sialon phosphor of the present embodiment satisfies one or both of the following (1) and (2).

[0059] (1) The density of crystal defects in the α-type sialon phosphor of the present embodiment can be 1.0 x 10 15 spins / g or less. The value is preferably 1.0 x 10 14 spins / g or more and 8.0 x 10 14 spins / g or less, more preferably 1.0 x 10 13 spins / g or more and 6.0 x 10 14 spins / g or less.

[0060] (2) The density of crystal defects in the α-type sialon phosphor of the present embodiment can be 1.0 x 10 15 spins / g or less. The value is preferably 1.0 x 10 14 spins / g or more and 8.0 x 10 14 spins / g or less, more preferably 1.0 x 10 13 spins / g or more and 6.0 x 10 14 spins / g or less.

[0061] The present inventors have studied the reasons for the change in the luminescent properties under a high-temperature environment from various viewpoints. Through the study, the present inventors have considered that the value of the density of crystal defects obtained by electron spin resonance (ESR) measurement can be related to the degree of change in the luminescent properties. This is because the presence of crystal defects generally causes a decrease in the luminescent properties.

[0062] The present inventors and the like have newly produced an α-type sialon phosphor in which the density of crystal defects obtained by electron spin resonance (ESR) measurement at 25°C and / or 200°C is sufficiently small, based on the above-described consideration. Then, by using this new α-type sialon phosphor as a wavelength conversion member for a white LED, it is possible to produce a white LED in which the luminescent properties are less likely to change even under a high-temperature environment.

[0063] The density of the crystal defects being sufficiently small at 200°C means a case where the crystal defects are few even in a high-temperature environment. It is considered that if the density of the crystal defects in a high-temperature environment is small, various characteristics in a high-temperature environment in a vehicle do not easily change, and thus the light emission characteristics do not easily change.

[0064] Also, if the density of the amorphous defects is sufficiently small even at 25°C, it is considered that there is a tendency that the crystal defects become fewer in a high-temperature environment in correspondence therewith. That is, if the density of the crystal defects is sufficiently small at 25°C, it is considered that the light emission characteristics do not easily change even in a high-temperature environment.

[0065] The α-type sialon phosphor of the present embodiment can be manufactured by going through appropriate manufacturing processes. Specifically, by going through two annealing processes, an N2 annealing process of annealing a powder-like α-type sialon phosphor in a nitrogen atmosphere and an H2 annealing process of annealing a powder-like α-type sialon phosphor in a hydrogen atmosphere, the α-type sialon phosphor of the present embodiment can be manufactured. In a case where the manufacturing method is inappropriate, the α-type sialon phosphor of the present embodiment cannot be obtained at times.

[0066] Details of the manufacturing method will be described later.

[0067] The description of the α-type sialon phosphor of the present embodiment is continued.

[0068] Composition of phosphor

[0069] The composition of the α-type sialon phosphor of the present embodiment can be expressed as follows, for example.

[0070] General formula: (M1 x , M2 y , Eu z )(Si 12-(m+n) Al m+n )(O n N 16-n ).

[0071] In the above general formula,

[0072] M1 is a 1-valent Li element,

[0073] M2 is a 2-valent element selected from one or more of the group consisting of Mg, Ca, and lanthanoid elements (excluding La and Ce),

[0074] 0≤x<2.0、0≤y<2.0、0<z≤0.5、0<x+y、0.3≤x+y+z≤2.0、0<m≤4.0、0<n≤3.0。

[0075] The solid solution composition of the α-sialon phosphor is represented by x, y, z in the above general formula, and m and n determined from the Si / Al ratio or the O / N ratio attached thereto. Especially in the case where M2 includes Ca, the α-sialon phosphor is stabilized in a wide range of composition, and a part thereof is substituted with Eu which becomes a luminescence center, so that a phosphor which exhibits yellow to orange visible light luminescence upon excitation with light in a wide range of wavelength region from ultraviolet to blue can be obtained.

[0076] Generally, the α-sialon phosphor is a second crystal phase different from the α-sialon phosphor or an amorphous phase inevitably present, so that the solid solution composition cannot be strictly specified by composition analysis or the like. As the crystal phase of the α-sialon phosphor, an α-sialon single phase is preferable, and aluminum nitride or a polytype thereof or the like can be included as another crystal phase.

[0077] • Properties of phosphor

[0078] The α-sialon phosphor is generally handled in the form of a collection of α-sialon phosphor particles, that is, an α-sialon phosphor powder.

[0079] The α-sialon phosphor particle generally includes a secondary particle in which a plurality of primary particles are aggregated into a lump.

[0080] The lower limit of the median particle diameter (D 50 ) of the α-sialon phosphor powder is preferably 1 μm or more, more preferably 5 μm or more, and further preferably 10 μm or more. Also, the upper limit of the median particle diameter of the α-sialon phosphor powder is preferably 30 μm or less, and more preferably 20 μm or less. The median particle diameter of the α-sialon phosphor powder is the size in the above secondary particle. That is, D 50 is preferably 1 μm or more and 30 μm or less, more preferably 5 μm or more and 30 μm or less, and further preferably 10 μm or more to 20 μm or less. By setting the median particle diameter of the α-sialon phosphor powder to 5 μm or more, the transparency of the wavelength conversion member can be further improved. On the other hand, by setting the median particle diameter of the α-sialon phosphor powder to 30 μm or less, the generation of chippings can be suppressed when the wavelength conversion member is subjected to cutting processing with a cutting machine or the like.

[0081] Here, the median particle diameter (D 50 ) of the α-sialon phosphor powder refers to the median particle diameter in the cumulative fraction based on the volume basis in accordance with the laser diffraction scattering method of JIS R1629: 1997. Incidentally, in the case where the α-sialon phosphor powder includes secondary particles, the median particle diameter obtained by the laser diffraction scattering method reflects the size of the secondary particles.

[0082] The shape of the α-sialon phosphor particle is not particularly limited. Shapes that can be mentioned include a spherical body, a cube, a columnar body, an irregular shape, and the like.

[0083] • Various properties at various temperatures

[0084] In addition to the density of crystal defects (spin density) at 25°C and 200°C described above, the performance of the α-type sialon phosphor at high temperatures can be further improved, in particular, by designing the α-type sialon phosphor in such a way as to satisfy one or more of the properties described below.

[0085] The density of crystal defects in the α-type sialon phosphor of the present embodiment is preferably 1.0 x 10 15 spins / g or less, more preferably 1.0 x 10 14 spins / g or more and 1.0 x 10 15 spins / g or less, further preferably 4.0 x 10 14 spins / g or more and 9.0 x 10 14 spins / g or less.

[0086] The density of crystal defects in the α-type sialon phosphor of the present embodiment is preferably 9.5 x 10 15 spins / g or less, more preferably 5.0 x 10 15 spins / g or more and 9.5 x 10 15 spins / g or less, further preferably 7.5 x 10 15 spins / g or more and 9.5 x 10 15 spins / g or less.

[0087] The internal quantum efficiency of the α-type sialon phosphor of the present embodiment at 200°C is preferably 87% or more, more preferably 88% or more. The closer the value is to 100%, the better, but in practice it is 95% or less or 93% or less. That is, the internal quantum efficiency at 200°C is preferably 87% or more and 95% or less, more preferably 88% or more and 93% or less.

[0088] The external quantum efficiency of the α-type sialon phosphor of the present embodiment at 300°C is preferably 80% or more, more preferably 82% or more. The closer the value is to 100%, the better, but in practice it is 90% or less or 88% or less. That is, the external quantum efficiency at 200°C is preferably 80% or more and 90% or less, more preferably 82% or more and 88% or less.

[0089] In the α-type sialon phosphor of the present embodiment, the internal quantum efficiency maintenance rate represented by {(internal quantum efficiency at 24°C) / (internal quantum efficiency at 300°C)} x 100[%] is preferably 89% or greater, more preferably 89% or greater and 99% or less, and further preferably 90% or greater and 99% or less.

[0090] In the α-type sialon phosphor of the present embodiment, the external quantum efficiency maintenance rate represented by {(external quantum efficiency at 24°C) / (external quantum efficiency at 300°C)} x 100[%] is preferably 88% or greater, more preferably 88% or greater and 99% or less, and further preferably 89% or greater and 97% or less.

[0091] <Light-emitting device>

[0092] Figure 1 is a schematic cross-sectional view illustrating the structure of a light-emitting device.

[0093] As shown in Figure 1 , the light-emitting device 100 includes a light-emitting element 120, a heat sink 130, a housing 140, a first lead frame 150, a second lead frame 160, a bonding wire 170, a bonding wire 172, and a composite body 40.

[0094] The light-emitting element 120 is mounted on a prescribed 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. Alternatively, a packaging substrate can be used instead of the heat sink 130.

[0095] 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 300 nm or greater and 500 nm or less, which corresponds to near-ultraviolet to blue light, can be used. One electrode (not shown) provided on the upper surface side of the light-emitting element 120 is connected to the surface of the first lead frame 150 via the bonding wire 170 such as a gold wire. Further, 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 the bonding wire 172 such as a gold wire.

[0096] A recess having a substantially funnel shape in which the aperture diameter gradually increases from the bottom surface toward the upper side is formed in the housing 140. The light-emitting element 120 is disposed on the bottom surface of the recess. The wall surface of the recess that surrounds the light-emitting element 120 functions as a reflection plate.

[0097] The composite 40 is filled in the recess formed by the housing 140. The composite 40 is a wavelength conversion member that lengthens the wavelength of excitation light emitted from the light emitting element 120. As the composite 40, the composite of the present embodiment is dispersed in the sealing material 30 such as a resin, and the phosphor 1 of the present embodiment. The light emitting device 100 emits a mixed color of light from the light emitting element 120 and light generated from the phosphor particles 1 that absorb and excite the light from the light emitting element 120. The light emitting device 100 preferably emits white light by color mixing of the light from the light emitting element 120 and the light generated from the phosphor 1.

[0098] Incidentally, as the resin that can be used in the sealing material 30 in the composite 40, transparent resins such as silicone resins, epoxy resins, and polyurethane resins can be given. The composite 40 can be produced, for example, by adding the α-type sialon phosphor of the present embodiment to a liquid resin or a powdered glass or ceramic and uniformly mixing, and then curing or sintering by heat treatment.

[0099] In the light emitting device 100 of the present embodiment, by using the α-type sialon phosphor described above as the phosphor 1, a change in light emitting characteristics at high temperatures is suppressed. Therefore, the light emitting device 100 can be preferably used for vehicle-mounted applications. However, it is first noted with caution that the use of the light emitting device 100 is not limited only to vehicle-mounted applications. The light emitting device 100 can also be applied to lighting applications or display device applications, and the like, which are not vehicle-mounted applications.

[0100] Incidentally, in the Figure 1 above, a surface mounting type light emitting device is exemplified, but the light emitting device is not limited to the surface mounting type, and can be a can type, a COB (Chip On Board) type, or a CSP (Chip Scale Package) type.

[0101] <Method for Producing α-Type Sialon Phosphor>

[0102] The method for producing the α-type sialon phosphor of the present embodiment includes the following steps:

[0103] A sintering step in which a block-shaped α-type sialon phosphor containing Eu is obtained by sintering;

[0104] A pulverization step in which the block-shaped α-type sialon phosphor is pulverized to obtain a powdered α-type sialon phosphor;

[0105] An N2annealing step in which the powdered α-type sialon phosphor is annealed at a temperature range of 1200°C or higher and 1700°C or lower and a time range of 5 hours or more and 30 hours or less in a nitrogen atmosphere;

[0106] H2annealing step of annealing the powder-like α-sialon phosphor after the N2annealing step in a hydrogen atmosphere at a temperature of 1200°C or higher and 1700°C or lower and a time of 5 hours or more and 30 hours or less.

[0107] acid treatment step of subjecting the powder-like α-sialon phosphor after the H2annealing step to acid treatment using an acidic aqueous solution.

[0108] In the production method of the α-sialon phosphor of the present embodiment, the H2annealing step is preferably performed after the N2annealing step.

[0109] Further, a elutriation step of classifying the powder-like α-sialon phosphor after the acid treatment step by elutriation is preferably performed.

[0110] By the production method as described above, an α-sialon phosphor having particularly few crystal defects can be obtained. Although the details are not clear, it is presumed that the combination of the N2annealing step and the H2annealing step is effective for reducing crystal defects.

[0111] Hereinafter, each step will be further described.

[0112] • sintering step

[0113] The sintering step can be performed by referring to the conventional production method of α-sialon phosphor. If one example is simply described, a block-like α-sialon phosphor containing Eu can be obtained by (i) first, mixing raw materials (nitride or oxide of each element, etc. that constitute an α-sialon phosphor containing Eu) to obtain a mixture; (ii) filling the mixture into a boron nitride container, and sintering at 1650°C or higher and 1950°C or lower in a nitrogen atmosphere.

[0114] Regarding the sintering step, for example, the description of paragraphs 0036 to 0044 and the description of the examples of International Publication No. 2020 / 203483 can be referred to. Further, the description of other known documents can also be referred to.

[0115] • pulverization step

[0116] In the sintering step, an α-sialon phosphor in the shape of an ingot is generally produced. By pulverizing the ingot-like α-sialon phosphor using a pulverizer such as a crusher, a mortar, a ball mill, a vibration mill, a jet mill, or the like, a powder-like α-sialon phosphor can be obtained.

[0117] By adjusting the degree of pulverization, the particle size distribution such as the median particle diameter of the α-sialon phosphor can be adjusted.

[0118] In addition to the pulverization process, a sieve classification process can be performed. By performing the sieve classification process, the particle size distribution such as the median particle diameter can be adjusted more precisely.

[0119] Further, a process of dispersing the pulverized powdery α-sialon phosphor in an aqueous solution and leaving it for a certain period of time to remove particles having a small particle diameter and being difficult to precipitate can be performed. Thereby, the particle size distribution such as the median particle diameter can be adjusted more precisely.

[0120] • N2annealing process

[0121] The temperature of the N2annealing process can be 1200°C or higher and 1700°C or lower, but is preferably 1300°C or higher and 1600°C or lower.

[0122] The time of the N2annealing process can be 5 hours or longer and 30 hours or shorter, but is preferably 8 hours or longer and 25 hours or shorter.

[0123] The pressure in the N2annealing process is not particularly limited, and for example, can be 0.02 MPa or higher and 0.9 MPa or lower, but is preferably 0.02 MPa or higher and 0.2 MPa or lower.

[0124] The N2annealing process can be performed in a mixed gas environment of N2and a non-reactive gas (noble gas or the like) other than N2, but is preferably performed in a gas environment consisting essentially of N2. Further, even in the mixed gas environment, the ratio of N2in the mixed gas is preferably more than 50% by volume, and more preferably more than 75% by volume. It is considered that in this way, the crystal defects in the α-sialon phosphor are further reduced.

[0125] • H2annealing process

[0126] The temperature of the H2annealing process can be 1200°C or higher and 1700°C or lower, but is preferably 1300°C or higher and 1600°C or lower.

[0127] The time of the H2annealing process can be 5 hours or longer and 30 hours or shorter, but is preferably 8 hours or longer and 25 hours or shorter.

[0128] The pressure in the H2annealing process is not particularly limited, and for example, can be 0.02 MPa or higher and 0.9 MPa or lower, but is preferably 0.02 MPa or higher and 0.1 MPa or lower.

[0129] The H2annealing process can be performed in a mixed gas environment of H2and a non-reactive gas (noble gas or the like) other than H2, but is preferably performed in a gas environment consisting essentially of H2. Also, even in the case of performing in a mixed gas environment, the ratio of H2in the mixed gas is preferably more than 50% by volume, and more preferably more than 75% by volume. It is considered that in this way, the crystal defects in the α-sialon phosphor are further reduced.

[0130] • Acid treatment process

[0131] In the acid treatment process, for example, the powder-like α-sialon phosphor is put into an acidic aqueous solution, and stirring is performed using a stirrer.

[0132] As the acidic aqueous solution, an acidic aqueous solution containing one acid selected from among hydrofluoric acid, nitric acid, hydrochloric acid, and the like, or a mixed acid aqueous solution obtained by mixing two or more of the above acids can be given. Among these, a hydrofluoric acid aqueous solution containing only hydrofluoric acid and a mixed acid aqueous solution obtained by mixing hydrofluoric acid and nitric acid are more preferable. The concentration of the stock solution of the acidic aqueous solution can be appropriately set according to the strength of the acid used, and is preferably 0.7% or more and 100% or less, and more preferably 0.7% or more and 40% or less. Also, the temperature at the time of performing the acid treatment is preferably 60°C or more and 90°C or less, and as the reaction time (immersion time), 15 minutes or more and 80 minutes or less are preferable.

[0133] By performing stirring at high speed, acid treatment of the particle surface is easily performed sufficiently. The "high speed" here depends on the stirring device used, but in the case of using a laboratory-level magnetic stirrer, the stirring speed is, for example, 400 rpm or more, and in practice, 400 rpm or more and 500 rpm or less. From the viewpoint of the usual purpose of stirring, which is to supply new acid to the particle surface at all times, a stirring speed of around 200 rpm is sufficient, but by performing high-speed stirring of 400 rpm or more, treatment of the particle surface is easily performed sufficiently not only by chemical action but also by physical action.

[0134] By selecting appropriate stirring conditions, foreign matter or heterogeneous phases on the surface of the phosphor, which can cause a decrease in luminescent properties, are removed sufficiently. As a result, it is considered that crystal defects as a whole of the α-sialon phosphor are further reduced. As a result, it is considered that the change in luminescent properties in a high-temperature environment can be further reduced.

[0135] • Classification process

[0136] In order to adjust the particle size distribution of the α-sialon phosphor, a certain classification treatment can be performed. The classification can be performed under dry conditions or under wet conditions. Various devices used in industry, such as a settling tank, a hydrocyclone, a centrifugal separator, a cyclone separator, an air separator, and the like can be used for the classification. Among these, elutriation classification based on a settling tank is preferred, and the specific method of classification is not limited to elutriation classification based on a settling tank.

[0137] The above describes the embodiments of the present application, but these are examples of the present application, and various structures other than the above can be employed. Also, the present application is not limited to the above-described embodiments, and modifications, and the like within a range capable of achieving the object of the present application are included in the present application.

[0138] Examples

[0139] The embodiments of the present application are described in detail based on examples and comparative examples. For the sake of caution, it is first noted that the present application is not limited to the examples.

[0140] Manufacture of α-sialon phosphor

[0141] (Examples 1 and 2 and Comparative Example 1)

[0142] An α-sialon phosphor was manufactured by the following steps.

[0143] (1) Firing step

[0144] In a glove box, as a blending composition of a raw material powder, silicon nitride powder (manufactured by Ube Industries, Ltd., E10 grade) was set to 62.4 parts by mass, aluminum nitride powder (manufactured by Tokuyama Corporation, E grade) was set to 22.5 parts by mass, europium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., RU grade) was set to 2.2 parts by mass, and calcium nitride powder (manufactured by Koju ndo Chemical Lab. Co., Ltd.) was set to 12.9 parts by mass, and after the raw material powders were dry-mixed, a nylon mesh having a mesh size of 250 μm was used to obtain a raw material mixed powder. 120 g of the raw material mixed powder was filled into a capped cylindrical boron nitride container (manufactured by DENKA COMPANY LIMITED, N-1 grade) having an internal volume of 0.4 liters.

[0145] The raw material mixed powder was subjected to a heat treatment (firing) at 1800°C for 16 hours in an electric furnace of a carbon heater under a nitrogen atmosphere at atmospheric pressure, together with the container. The calcium nitride contained in the raw material mixed powder is easily hydrolyzed in air, so after the boron nitride-made container filled with the raw material mixed powder was taken out of the glove box, it was quickly put into the electric furnace, and immediately subjected to vacuum exhaust, thereby preventing the reaction of the calcium nitride.

[0146] (2) Pulverization step

[0147] The fired product obtained in the above (1) was pulverized or crushed with a mortar as appropriate, and made to pass through a sieve having a mesh size of 150 μm, to obtain a phosphor powder. As a result of investigating the crystal phase of the phosphor powder by powder X-ray diffraction using CuKα rays, the crystal phase present was α-sialon.

[0148] (3) N2annealing step

[0149] The powder-like α-sialon phosphor obtained in the pulverization step of the above (2) was put into a boron nitride-made container and covered with a lid. The container was put into a heating furnace, and subjected to a heat treatment under a nitrogen atmosphere under the conditions described in the column of "N2annealing" in Table 1 below. After natural cooling, the orange powder recovered from the container was made to pass through a sieve having a mesh size of 75 μm. Thus, a phosphor powder subjected to N2annealing was obtained.

[0150] (4) H2annealing step

[0151] The phosphor powder subjected to N2annealing of the above (3) was put into a boron nitride-made container and covered with a lid. The container was put into a heating furnace, and subjected to a heat treatment under a hydrogen atmosphere. The heating conditions were set to the conditions described in the column of "H2annealing" in Table 1 below. After natural cooling, the orange powder recovered from the container was made to pass through a sieve having a mesh size of 75 μm. Thus, a phosphor powder subjected to H2annealing was obtained.

[0152] (5) Acid treatment step

[0153] First, 50% hydrofluoric acid 50 mL and 70% nitric acid 50 mL were mixed to make a mixed stock solution. To the mixed stock solution, distilled water 300 mL was added, and the concentration of the mixed stock solution was diluted to 25%, to prepare an acid aqueous solution 400 mL.

[0154] To the acid aqueous solution, the phosphor powder 30 g recovered after the H2annealing step of the above (4) was added, and the temperature of the acid aqueous solution was maintained at 80°C, and stirred using a magnetic stirrer at a rotation speed of 450 rpm for 60 minutes.

[0155] After the stirring, the acid adhering to the phosphor was washed thoroughly with distilled water. The washed phosphor powder was recovered by filtration and dried.

[0156] The particle size distribution of the dried phosphor powder was measured using a Microtrac MT3300EXII (MicrotracBEL Corp.) by a laser diffraction scattering method in accordance with JIS R1629:1997.

[0157] Specifically, first, 0.5 g of the powdery α-sialon phosphor was put into 100 cc of ion-exchanged water, and a dispersion treatment was performed for 3 minutes using an Ultrasonic Homogenizer US-150E (NIHON SEIKI KAI SHA LTD., chip size φ 20 mm, Amplitude 100%, oscillation frequency 19.5 kHz, amplitude about 31 μm) to obtain a dispersion liquid. The dispersion liquid was set in the MT3300EXII, and the particle size distribution was measured.

[0158] From the obtained particle size distribution, the median particle diameter D 50 .

[0159] The conditions of the N2annealing step and the H2annealing step and D 50 are shown in Table 1.

[0160] [Table 1]

[0161] Table 1

[0162]

[0163] <ESR Measurement>

[0164] The ESR measurement was performed on the α-sialon phosphors of Examples 1, 2 and Comparative Example 1 as follows. Then, the density of crystal defects of the α-sialon phosphor at 25°C, 200°C, 300°C and 600°C was obtained as the value of the spin density of the signal in the vicinity of g = 2.

[0165] (Measurement Procedure)

[0166] The sample powder (about 60 mg) was put into an ESR sample tube and set in the apparatus, and the ESR measurement in the vicinity of g = 2 was performed at room temperature (25°C) while causing simulated air (flow rate: 20 mL min"1) to flow through the sample tube.

[0167] After that, the temperature was raised at a rate of 30°C / minute to 200°C, and after keeping it for 30 minutes, the ESR measurement in the vicinity of g = 2 was performed.

[0168] Further, after temperature increase at a rate of 30°C / min to 300°C, ESR measurement was performed in the vicinity of g = 2 after 30 minutes of holding.

[0169] Further, after temperature increase at a rate of 30°C / min to 600°C, ESR measurement was performed in the vicinity of g = 2 after 30 minutes of holding.

[0170] (Measurement device and measurement conditions)

[0171] An ESR device "EMXplus" manufactured by BRUKER and a high temperature cavity "ER4114HT" manufactured by BRUKER were used. Further, the measurement conditions were as follows.

[0172] Magnetic field sweep range: in the vicinity of 3350 to 3550 G

[0173] Modulation: 100 kHz, 5 G

[0174] Microwave: 9.67 GHz, 1 mW

[0175] Sweep time: 80 s x 4 times

[0176] Time constant: 327.68 ms

[0177] Data points: 1000 points

[0178] (Analysis of measurement data)

[0179] The ESR spectrum is generally observed as a first order differential curve in order to sensitively observe the concave-convex of the absorption spectrum of electromagnetic waves. Since the absorption intensity is proportional to the number of spins, the ESR spectrum is twice integrated and the differential curve is changed to an integral curve, and the number of spins of the sample is quantified based on the peak area ratio to a standard sample.

[0180] Regarding the integral range, in the first order differential curve, after subtraction with a straight line passing through the vicinity of g = 2.0171 and the vicinity of g = 1.9838 as a baseline, the range of g = 2.0171 to 1.9838 was integrated. Thereby, the peak area of the sample derived from the vicinity of g = 2 was calculated.

[0181] The ESR software "WinEPR" manufactured by BRUKER was used at the time of analysis.

[0182] (Calculation of the number of spins and spin density)

[0183] The number of spins at 25°C of the sample was calculated by multiplying the number of spins at 25°C of the secondary standard sample (ion-implanted polyethylene film) by the ratio of the peak area of the sample to that of the secondary standard sample. Further, the number of spins per unit mass of the sample at 25°C (spin density [spins / g]) was calculated by dividing the number of spins of the sample by the mass [g] of the sample to be measured.

[0184] Incidentally, the number of spins of the secondary standard sample (ion-implanted polyethylene film) was calculated by additionally performing ESR measurement on a primary standard sample (copper sulfate pentahydrate) whose number of spins was known at 25°C, and from the ratio of the peak area thereof.

[0185] The number of spins at 200°C of the sample was calculated by multiplying the number of spins at 200°C of the secondary standard sample (ion-implanted polyethylene film) by the ratio of the peak area of the sample to that of the secondary standard sample, after which the same method as in the case of 25°C was performed, and the effect of the measurement temperature on the signal intensity was corrected by multiplying the measurement temperature ((273 + 200) [K]) ÷ room temperature ((273 + 25) [K]) (Curie's law). Further, the number of spins per unit mass of the sample at 200°C (spin density [spins / g]) was calculated by dividing the number of spins of the sample by the mass [g] of the sample to be measured.

[0186] Similarly, the spin density [spins / g] of the sample at 300°C was calculated. Incidentally, when performing temperature correction based on Curie's law, the measurement temperature ((273 + 300) [K]) ÷ room temperature ((273 + 25) [K]) was multiplied.

[0187] Similarly, the spin density [spins / g] of the sample at 600°C was calculated. Incidentally, when performing temperature correction based on Curie's law, the measurement temperature ((273 + 600) [K]) ÷ room temperature ((273 + 25) [K]) was multiplied.

[0188] (Supplement)

[0189] The absorption intensity in the ESR spectrum varies depending on the measurement conditions. Therefore, the effects of the Q value of the resonator, the reception gain, the number of accumulations [times], the modulation [G], the conversion time [ms], the microwave power [mW], the inner diameter of the sample tube [mm], the center position of the resonator [mm], the length of the sample inserted [mm], and the number of spins were appropriately corrected at the time of analysis.

[0190] The results are shown in Table 2 below. The unit of the numerical values is spins / g.

[0191] [Table 2]

[0192] Table 2

[0193] [Table 2]

[0194] Evaluation: Change in Luminescent Properties Based on Temperature

[0195] With respect to the α-sialon phosphors of each of the examples and comparative examples, the absorption rate, internal quantum efficiency, and external quantum efficiency were calculated by subtracting re-excitation fluorescence from the overall fluorescence using a spectrophotometer (QE-2100 manufactured by Otsuka Electronics Co., Ltd.), and re-excitation method correction was performed with respect to the absorption rate, internal quantum efficiency, and external quantum efficiency and their temperature dependence.

[0196] The absorption rate, internal quantum efficiency, and external quantum efficiency were calculated by changing the sample temperature from room temperature to 300°C, and the temperature change in the internal quantum efficiency and external quantum efficiency was evaluated.

[0197] As a quantitative index of the temperature change, the internal quantum efficiency at each temperature relative to the value of the internal quantum efficiency at room temperature, "internal quantum efficiency maintenance rate", and the external quantum efficiency at each temperature relative to the value of the external quantum efficiency at room temperature, "external quantum efficiency maintenance rate", were calculated.

[0198] The above evaluation results are summarized in Tables 3, 4, and 5.

[0199] [Table 3]

[0200]

[0201] [Table 4]

[0202]

[0203] [Table 5]

[0204]

[0205] As understood from the above tables, the density of crystal defects at 25°C or 200°C is greater than 1.0 x 10 15 In Comparative Example 1 of spin s / g, the internal quantum efficiency and external quantum efficiency decreased significantly, particularly at a high temperature of 300°C.

[0206] On the other hand, in Examples 1 and 2 in which the density of crystal defects at 25°C or 200°C is 1.0 x 10 15 In Examples 1 and 2 in which the density of crystal defects at 25°C or 200°C is 1.0 x 10

[0207] This application claims priority based on Japanese Patent Application No. 2023-058890 filed on March 31, 2023, the disclosure of which is incorporated herein in its entirety.

[0208] Symbol Explanation

[0209] 1 phosphor

[0210] 30 sealing material

[0211] 40 composite

[0212] 100 light emitting device

[0213] 120 light emitting element

[0214] 130 heat sink

[0215] 140 housing

[0216] 150 first lead frame

[0217] 160 second lead frame

[0218] 170 bonding wire

[0219] 172 bonding wire

Claims

1. An α-sialon phosphor containing an Eu element, wherein The density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

2. An α-sialon phosphor containing an Eu element, wherein The density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

3. The α-sialon phosphor according to claim 2, wherein The density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

4. The α-sialon phosphor according to any one of claims 1 to 3, wherein The density of crystal defects in the α-type sialon phosphor is 1.0 x 10 15 spins / g or less.

5. The α-sialon phosphor according to any one of claims 1 to 3, wherein The density of crystal defects in the α-type sialon phosphor was 9.5 x 10 15 spins / g or less.

6. The α-sialon phosphor according to any one of claims 1 to 3, which has an internal quantum efficiency of 87% or more at 200°C.

7. The α-sialon phosphor according to any one of claims 1 to 3, which has an internal quantum efficiency of 80% or more at 300°C.

8. The α-sialon phosphor according to any one of claims 1 to 3, wherein a retention rate of internal quantum efficiency represented by {(internal quantum efficiency at 24°C) / (internal quantum efficiency at 300°C)} x 100[%] is 89% or more.

9. The α-sialon phosphor according to any one of claims 1 to 3, wherein a retention rate of external quantum efficiency represented by {(external quantum efficiency at 24°C) / (external quantum efficiency at 300°C)} x 100[%] is 88% or more.

10. The α-sialon phosphor according to any one of claims 1 to 3, wherein Composition is represented by the general formula: (M1 x , M2 y , Eu z )(Si 12-(m+n) Al m+n )(O n N 16-n ) in the general formula, M1 is a 1-valent Li element, M2 is one or more 2-valent elements selected from the group consisting of Mg, Ca, and lanthanoid elements other than La and Ce, 0≤x<2.0, 0≤y<2.0, 0<z≤0.5, 0<x+y, 0.3≤x+y+z≤2.0, 0<m≤4.0, 0<n≤3.

0.

11. A light emitting device comprising: a light emitting element; and a wavelength conversion section including the α-sialon phosphor according to any one of claims 1 to 3, and wavelength-converts light emitted from the light emitting element.

12. A method for producing an α-sialon phosphor, comprising the following steps: a firing step of obtaining a block-shaped α-sialon phosphor containing an Eu element by firing; a pulverization step of pulverizing the block-shaped α-sialon phosphor to obtain a powder-shaped α-sialon phosphor; an N2 annealing step of annealing the powder-shaped α-sialon phosphor in a nitrogen atmosphere at a temperature range of 1200°C or higher and 1700°C or lower and a time range of 5 hours or more and 30 hours or less; an H2 annealing step of annealing the powder-shaped α-sialon phosphor in a hydrogen atmosphere at a temperature range of 1200°C or higher and 1700°C or lower and a time range of 5 hours or more and 30 hours or less; and an acid treatment step of subjecting the powder-shaped α-sialon phosphor after the H2 annealing step to acid treatment using an acidic aqueous solution.

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