HK1237809A

HK1237809A - Method of producing nitride fluorescent material, nitride fluorescent material, and light-emitting device using the same

Info

Publication number: HK1237809A
Application number: HK17111891.8A
Authority: HK
Inventors: 涌井贞一; 细川昌治
Original assignee: 日亚化学工业株式会社
Priority date: 2015-11-11
Filing date: 2017-11-16
Publication date: 2018-04-20

Description

Method for producing nitride phosphor, and light-emitting device

Technical Field

The invention relates to a method for producing a nitride phosphor, and a light-emitting device.

Background

A Light Emitting device including a combination of a Light Emitting Diode (hereinafter referred to as "LED") and a phosphor has been widely used in a lighting device, a backlight of a liquid crystal display device, and the like. For example, when the light-emitting device is used in a liquid crystal display device, a phosphor having a narrow half-value width is preferably used in order to increase the color reproduction range.

Such a phosphor includes red-emitting SrLiAl₃N₄Eu (hereinafter, also referred to as "SLAN phosphor"). For example, patent document 1 and non-patent document 1(Philipp Pust et al, "Narrow-band red-emitting SrLiAl₃N₄]:Eu²⁺as a next-generation LED-phosphor Materials "Nature Materials, NMAT4012, VOL13September 2014), discloses a SLAN phosphor having a narrow half-value width of 70nm or less and an emission peak wavelength of around 650 nm.

As disclosed in non-patent document 1, the SLAN phosphor can be produced as follows: lithium aluminum hydride (LiAlH) was weighed in a stoichiometric ratio such that Eu became 0.4 mol%₄) Aluminum nitride (AlN), strontium hydride (SrH)₂) And europium fluoride (EuF)₃) The raw material powder of (3) is mixed and then charged into a crucible, and fired at 1000 ℃ for 2 hours under the atmospheric pressure of a mixed gas atmosphere of hydrogen and nitrogen.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2015-526532

Non-patent document

Non-patent document 1: philipp Pust et al, "Narrow-band red-emitting Sr [ LiAl₃N₄]:Eu²⁺as a next-generation LED-phosphor material”Nature Materials,NMAT4012,VOL13September 2014

Disclosure of Invention

Problems to be solved by the invention

However, there is room for further improvement in the emission intensity of the SLAN phosphor. The invention aims to provide a method for producing a nitride phosphor capable of obtaining a nitride phosphor having high luminous intensity, a nitride phosphor, and a light-emitting device.

Means for solving the problems

The present invention includes the following embodiments, as described below.

A first embodiment of the present invention relates to a method for producing a nitride phosphor containing a fired product having a composition represented by the following formula (I) and having an oxygen element content of 2 to 4 mass%,

wherein, the manufacturing method comprises the following steps: a step of preparing a fired product having a composition represented by the formula (I), and mixing the fired product with a polar solvent having a relative dielectric constant at 20 ℃ of 10 to 70 inclusive.

M^a _vM^b _wM^c _xM^d _yN_z(I)

(in the formula (I), M^aIs at least 1 element selected from Sr, Ca, Ba and Mg, M^bIs at least 1 element selected from Li, Na and K, M^cIs at least 1 element selected from Eu, Mn, Tb and Ce, M^dIs at least 1 element selected from Al, B, Ga and In, and v, w, x, y and z are numbers satisfying 0.8. ltoreq. v.ltoreq.1.1, 0.8. ltoreq. w.ltoreq.1.1, 0.001. ltoreq. x.ltoreq.0.1, 2.0. ltoreq. y.ltoreq.4.0, and 3.0. ltoreq. z.ltoreq.5.0, respectively. )

A second embodiment of the present invention relates to a method for producing a nitride phosphor, which includes the steps of preparing a fired product having a composition represented by the following formula (I), mixing the fired product with a polar solvent,

the polar solvent is an alcohol and/or a ketone containing 0.01 to 12 mass% of water.

M^a _vM^b _wM^c _xM^d _yN_z(I)

(in the formula (I), M^aIs at least 1 element selected from Sr, Ca, Ba and Mg, M^bIs at least 1 element selected from Li, Na and K, M^cIs at least 1 element selected from Eu, Mn, Tb and Ce, M^dIs at least 1 element selected from Al, B, Ga and In, and v, w, x, y and z are each fullV is more than or equal to 0.8 and less than or equal to 1.1, w is more than or equal to 0.8 and less than or equal to 1.1, x is more than or equal to 0.001 and less than or equal to 0.1, y is more than or equal to 2.0 and less than or equal to 4.0, and z is more than or equal to 3.0 and less than or equal to 5.0. )

A third embodiment of the present invention relates to a nitride phosphor containing a fired product having a composition represented by the following formula (I) and having an oxygen element content of 2 mass% or more and 4 mass% or less.

M^a _vM^b _wM^c _xM^d _yN_z(I)

A fourth embodiment of the present invention relates to a light-emitting device including a nitride phosphor and an excitation light source. ADVANTAGEOUS EFFECTS OF INVENTION

According to one embodiment of the present invention, a method for producing a nitride phosphor, and a light-emitting device, which can obtain a nitride phosphor having high emission intensity, can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a light-emitting device.

[ FIG. 2]]FIG. 2 shows X-ray diffraction patterns of nitride phosphors of examples and comparative examples of the present invention and Sr₃Al₂(OH)₁₂、LiAl₂(OH)₇·2H₂O、SrLiAl₃N₄The X-ray diffraction pattern of the compound (SLAN) shown below.

Fig. 3 is a graph showing emission spectra of relative emission intensities with respect to wavelength for nitride phosphors of examples and comparative examples of the present invention.

FIG. 4 is an SEM photograph of the nitride phosphor of example 1.

FIG. 5 is an SEM photograph of the nitride phosphor of example 4.

FIG. 6 is an SEM photograph of a nitride phosphor of comparative example 6.

Description of the symbols

10: light emitting element

50: sealing member

71: first phosphor

72: second phosphor

100: light emitting device

Detailed Description

The method for producing a nitride phosphor, the nitride phosphor, and the light-emitting device according to the present invention will be described below with reference to embodiments. The embodiments described below are examples provided to embody the technical idea of the present invention, and the present invention is not limited to the following method for producing a nitride phosphor, and light-emitting device. The relationship between the color name and the chromaticity coordinate, the relationship between the wavelength range of light and the color name of monochromatic light, and the like are performed in accordance with JIS Z8110. In addition, the content of each component in the composition indicates the total amount of a plurality of substances present in the composition, when the plurality of substances corresponding to each component are present in the composition, unless otherwise specified.

[ method for producing nitride phosphor ]

A method for producing a nitride phosphor according to an embodiment of the present invention is a method for producing a nitride phosphor containing a fired product having a composition represented by the following formula (I) and having an oxygen element content of 2 mass% or more and 4 mass% or less, the method including: a step of preparing a fired product having a composition represented by the formula (I), and mixing the fired product with a polar solvent having a relative dielectric constant at 20 ℃ of 10 to 70 inclusive.

M^a _vM^b _wM^c _xM^d _yN_z(I)

Here, in the formula (I), M^aIs at least 1 element selected from Sr, Ca, Ba and Mg, M^bIs at least 1 element selected from Li, Na and K, M^cIs at least 1 element selected from Eu, Mn, Tb and Ce, M^dAt least 1 element selected from Al, Si, B, Ga, In, Ge and Sn, particularly preferably at least 1 element selected from Al, B, Ga and In, and v, w, x, y and z are numbers satisfying 0.8. ltoreq. v.ltoreq.1.1, 0.8. ltoreq. w.ltoreq.1.1, 0.001. ltoreq. x.ltoreq.0.1, 2.0. ltoreq. y.ltoreq.4.0, 3.0. ltoreq. z.ltoreq.5.0, respectively.

In addition, a method for producing a nitride phosphor according to an embodiment of the present invention includes: a step of preparing a fired product having a composition represented by the formula (I), and mixing the fired product with a polar solvent, wherein the polar solvent is an alcohol and/or a ketone containing 0.01 to 12 mass% of water.

In the method for producing a nitride phosphor according to the present embodiment, M is preferably in the composition represented by formula (I) above^aContaining at least one of Sr and Ca, M^bContaining Li, M^cIs Eu, M^dIs Al.

The production method of the present embodiment includes a step of mixing the particulate fired product obtained by the heat treatment with the polar solvent.

The phosphor obtained by the production method of the present embodiment is considered to be capable of forming, for example, a hydroxide or an oxide on the surface or at least a part of the vicinity of the surface of the fired product particles by water contained in the polar solvent while dispersing the particles as the fired product by mixing the fired product having the composition represented by the formula (I) with the polar solvent. Thus, it is considered that light can be efficiently extracted from the inside of the phosphor particles by adjusting, for example, the refractive index in the vicinity of the surface of the phosphor particles, and as a result, the emission intensity of the phosphor can be improved.

[ Process for preparing fired product ]

The manufacturing method of the present embodiment includes: in order to obtain a fired product, a raw material mixture obtained by mixing the respective raw materials is used, and the raw material mixture is subjected to a heat treatment to prepare a fired product represented by the above formula (I).

(raw material mixture)

The material contained in the raw material mixture used in the production method of the present embodiment is not particularly limited as long as a fired product having the composition represented by the above formula (I) can be obtained. For example, the raw material mixture may contain at least 1 raw material selected from the simple substances of the metal elements constituting the composition represented by the above formula (I) and their metal compounds. Examples of such metal compounds include: hydrides, nitrides, fluorides, oxides, carbonates, chlorides, and the like. The raw material is preferably at least 1 selected from the group consisting of hydride, nitride, and fluoride, from the viewpoint of improving the light-emitting characteristics. When the raw material mixture contains an oxide, a carbonate, a chloride, or the like as a metal compound, the content thereof is preferably 5% by mass or less, more preferably 1% by mass or less, in the raw material mixture. Among the metal compounds, fluoride or chloride may be added to the raw material mixture as a compound in which the element ratio of the cation has a target composition, and may also have an effect as a flux component described later.

The following metal compounds are preferably contained in the raw material mixture: as M^aAnd a metal compound containing a metal element selected from Sr, Ca, Ba and Mg as M^bAnd gold containing a metal element selected from Li, Na and KOf compounds of the genus as M^cAnd a metal compound containing a metal element selected from Eu, Mn, Tb and Ce, and M^dAnd a metal compound containing a metal element selected from the group consisting of Al, Si, B, Ga, In, Ge and Sn.

As the metal element (M) containing one or more elements selected from Sr, Ca, Ba and Mg^aElement) (hereinafter also referred to as "first metal compound") includes, specifically: SrN₂、SrN、Sr₃N₂、SrH₂、SrF₂、Ca₃N₂、CaH₂、CaF₂、Ba₃N₂、BaH₂、BaF₂、Mg₃N₂、MgH₂、MgF₂Preferably, at least 1 selected from these.

The first metal compound preferably includes at least one of Sr and Ca. In the case where the first metal compound contains Sr, a part of Sr is optionally substituted with Ca, Mg, Ba, or the like. When the first metal compound contains Ca, a part of Ca is optionally substituted with Sr, Mg, Ba, or the like. Thus, the emission peak wavelength of the nitride phosphor can be adjusted.

The first metal compound may be a monomer, or a compound such as an imide compound or an amide compound may be used. The first metal compound may be used alone in 1 kind, or 2 or more kinds may be used in combination.

Containing a metal element (M) selected from Li, Na and K^bElement) (hereinafter also referred to as "second metal compound") preferably contains at least Li, and more preferably at least 1 of a nitride and a hydride of Li. When the second metal compound contains Li, a part of Li is optionally substituted with Na, K, or the like, and may contain another metal element constituting the nitride phosphor.

As the second metal compound containing Li, Li is particularly preferably selected from Li₃N、LiN₃LiH and LiAlH₄At least 1 kind of (1).

Containing a metal element (M) selected from the group consisting of Al, Si, B, Ga, In, Ge and Sn^dElement) (hereinafter also referred to as "third metal compound") may be a metal compound substantially containing only a metal element selected from Al, Si, B, Ga, In, Ge, and Sn as its metal element, or may be a metal compound In which a part of a metal element is replaced with another metal element. The third metal compound is preferably a metal compound containing Al alone, may be a metal compound In which Al is partially substituted with another metal element selected from Ga and In which the group 13 element is present, V, Cr and Co In the fourth period, and the like, or may be a metal compound containing Li and other metal elements constituting the nitride phosphor In addition to Al.

As the third metal compound, specific examples of the metal compound containing Al include AlN and AlH₃、AlF₃、LiAlH₄And the like, preferably at least 1 selected from these.

The third metal compound may be used alone in 1 kind, or 2 or more kinds may be used in combination.

Containing a metal element (M) selected from Eu, Mn, Tb and Ce^cElement) may be a metal compound substantially containing only a metal element selected from Eu, Mn, Tb, and Ce as its metal element, or may be a metal compound in which a part of the metal element is replaced with another metal element.

The fourth metal compound is preferably a metal compound containing Eu, and may contain Eu as an activator, and part of Eu is replaced with Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or the like. It is considered that, by replacing a part of Eu with another element, the other element can function as, for example, a co-activator. By using the co-activator, the emission characteristics of the nitride phosphor can be adjusted. When a mixture in which Eu is required is used as the nitride phosphor, the mixing ratio may be changed as necessary. Europium predominantly has the energy of valency 2 and 3At least Eu, the nitride phosphor of the present embodiment²⁺Used as an activator.

As the fourth metal compound, a metal compound containing Eu includes Eu₂O₃、EuN、EuF₃And the like, preferably at least 1 selected from these. The nitride phosphor according to the present embodiment contains Eu in valence 2 as a center of light emission, but Eu in valence 2 is easily oxidized, and a metal compound containing Eu in valence 3 may be used to constitute the raw material mixture.

The raw material mixture may contain, in addition to the above-mentioned simple metal elements and metal compounds, other metal elements other than these, as required. The other metal element may be usually in the form of an oxide, a hydroxide, or the like to form the raw material mixture, but is not limited thereto, and may be a simple metal, a nitride, an imide, an amide, another inorganic salt, or the like, or may be contained in the raw material mixture in advance.

The raw material mixture may also contain a flux (flux). When the flux is contained in the raw material mixture, the reaction between the raw materials is further promoted, and the solid-phase reaction proceeds more uniformly, whereby a phosphor having a large particle size and more excellent light emission characteristics can be obtained. This is considered to be because, for example, when the heat treatment in the production method is performed at 1000 ℃ or higher and 1300 ℃ or lower, the temperature is substantially the same as the generation temperature of the liquid phase of the halide when the halide or the like is used as the flux. As the halide used as the flux, chlorides, fluorides, and the like of rare earth metals, alkaline earth metals, and alkali metals can be used. The flux may be added to the raw material mixture in the form of a compound in which the element ratio of the cations reaches the target composition, or may be added in the form of a compound in which each raw material is added to the target composition. Particular preference is given to fluoride.

When the raw material mixture contains a flux, the flux component promotes reactivity, but if it is too large, the reactivity may be improved due to workability in the production process of the nitride phosphorAnd the emission intensity of the obtained nitride phosphor is reduced. Therefore, the content of the flux in the raw material mixture is, for example, preferably 10 mass% or less, and more preferably 5 mass% or less. The raw material mixture may comprise, for example, SrF₂、EuF₃Such fluorides. When such a fluoride is used, the content of the fluorine element contained in the final phosphor is preferably 0.1 mass% or more and 1 mass% or less.

(Heat treatment)

The manufacturing method of the present embodiment includes: the raw material mixture was subjected to heat treatment in a nitrogen atmosphere to prepare a fired product having a composition represented by the formula (I).

The fired product having the composition represented by formula (I) can be prepared by subjecting the mixture mixed with the raw materials to a heat treatment in a nitrogen-containing gas atmosphere at a temperature of 1000 ℃ to 1400 ℃ inclusive and a pressure of 0.2MPa to 200MPa inclusive, for example.

By heat-treating the raw material mixture at a predetermined temperature in a pressurized gas atmosphere containing nitrogen, a particulate fired product having a desired composition and high luminous intensity can be efficiently produced. The particles of the fired product can also be used as phosphor particles.

The raw material mixture prepared so as to have the composition represented by formula (I) above is subjected to a heat treatment to obtain a fired product. The heat treatment may use, for example, a gas pressurized electric furnace. The heat treatment temperature may be in the range of 1000 ℃ to 1400 ℃, preferably 1000 ℃ to 1300 ℃, more preferably 1100 ℃ to 1300 ℃. When the heat treatment temperature is 1000 ℃ or higher, a fired product having the above-mentioned composition ratio can be formed, and when the temperature is 1400 ℃ or lower, decomposition of the fired product does not occur, and there is no possibility that the light emission characteristics of the nitride phosphor obtained from the fired product are deteriorated.

The heat treatment may be a first-stage heat treatment performed at 800 ℃ to 1000 ℃ inclusiveAnd a second stage of heat treatment is performed at 1000 ℃ or higher and 1400 ℃ or lower by slowly raising the temperature (multi-step firing). The heat treatment of the raw material mixture may be performed by using a carbon material such as graphite, a Boron Nitride (BN) material, or alumina (Al)₂O₃) And W, Mo crucible and boat.

The heat treatment gas atmosphere is preferably a gas atmosphere containing nitrogen, and the gas atmosphere containing nitrogen may be a gas atmosphere containing at least 1 selected from hydrogen, argon, carbon dioxide, carbon monoxide, ammonia, and the like in addition to nitrogen. The ratio of nitrogen gas in the heat treatment gas atmosphere is preferably 70 vol% or more, and more preferably 80 vol% or more.

The heat treatment is preferably performed in a pressurized gas atmosphere of 0.2MPa or more and 200MPa or less. The target nitride phosphor is more easily decomposed as the temperature is increased, but the decomposition is suppressed by forming the pressurized gas atmosphere, and a higher light emission intensity can be realized. The pressurized gas atmosphere is preferably 0.2MPa or more and 1.0MPa or less, more preferably 0.8MPa or more and 1.0MPa or less in gauge pressure. By increasing the pressure of the atmosphere gas during the heat treatment, the decomposition of the phosphor compound during the heat treatment can be suppressed, and a phosphor having high emission characteristics can be obtained.

The time of the heat treatment may be appropriately selected depending on the heat treatment temperature, gas pressure, and the like. The time for the heat treatment is, for example, 0.5 hours or more and 20 hours or less, preferably 1 hour or more and 10 hours or less.

Next, as an example of the production method of the present embodiment, Sr, which is a material capable of obtaining a nitride phosphor containing a fired product having a composition represented by the above formula (I), is used_0.993Eu_0.007LiAl₃N₄The method for producing the fired product having the designed composition will be specifically described, but the method for producing the nitride phosphor is not limited to the following production method.

SrN was used as the metal compound constituting the raw material mixture_u(corresponding to u-2/3, SrN)₂And SrN), LiAlH₄、AlN、EuF₃Each powder of (a) was weighed so that Sr: Eu: Li: Al was 0.9925:0.0075:1.2:3 in a glove box in an inert gas atmosphere. These powders were mixed to obtain a raw material mixture. Here, Li is likely to scatter during firing, and therefore is blended slightly more than the theoretical composition. The present embodiment is not limited to the above composition ratio.

Sr can be obtained by heat-treating the above raw material mixture in a nitrogen atmosphere_0.993Eu_0.007LiAl₃N₄The particle-like fired product shown. However, the ratio of the elements in the composition formula is a theoretical composition ratio estimated from the blending ratio of the raw material mixture. The coefficients of the respective elements are removed from the composition formula. Some of the elements such as F, which are scattered during firing, are also removed from the composition formula. As described above, the actual composition contains a certain amount of oxygen element. Further, by using a fluoride which also exerts an effect as a flux component, a certain amount of fluorine element is contained in the fired product. The Sr, Eu, and Li ratio in the composition formula is a value calculated based on the composition ratio of Al as 3. The charge ratio of Sr, Eu, and Li may be different from the theoretical composition ratio because decomposition, scattering, and the like occur during heat treatment. Further, by changing the blending ratio of each raw material, a nitride phosphor having a desired composition can be obtained.

In addition, other manufacturing methods than the above-described method may be used. The fired product having the target composition represented by the above formula (I) can be produced as follows: the alloy is pulverized after weighing the metal simple substances of the respective elements so as to have a predetermined composition ratio, and the pulverized alloy is fired in a gas pressure sintering furnace or a Hot Isostatic Pressing (HIP) furnace using a HIP method in a nitrogen atmosphere.

[ mixing Process of fired product and polar solvent ]

The production method of the present embodiment includes a step of mixing a fired product having a composition represented by the above formula (I) with a polar solvent.

The production method of the present embodiment disperses the particles of the fired product by the step of mixing the fired product having the composition represented by the above formula (I) with the polar solvent. In this process, it is considered that at least a part of the particle surface of the fired product is affected by the polar solvent to form, for example, a hydroxide or an oxide on the particle surface of the fired product. It is considered that the phosphor obtained in this way has a compound having a composition different from that of the phosphor at least in part of the surface, and thus light can be efficiently extracted by adjusting, for example, the refractive index in the vicinity of the surface of the phosphor particle, and as a result, the emission intensity of the phosphor can be improved.

Further, the production method of the present embodiment includes a step of mixing the particles of the fired product having the composition represented by the above formula (I) with a polar solvent, and can be carried out while satisfying both dispersion of the particles of the fired product and adjustment of the refractive index on the surface of the particles of the fired product, and therefore, a nitride phosphor having high emission intensity can be efficiently produced.

(polar solvent)

In the production method according to the embodiment of the present invention, the polar solvent is a polar solvent having a relative dielectric constant of 10 or more and 70 or less at 20 ℃, or an alcohol and/or a ketone containing 0.01% by mass or more and 12% by mass or less of water.

The polar solvent has a relative dielectric constant at 20 ℃ of preferably 10 or more, more preferably 15 or more. The polar solvent preferably has a relative dielectric constant of 35 or less at 20 ℃.

When the polar solvent is an alcohol and/or a ketone containing 0.01 to 12 mass% of water, the relative dielectric constant at 20 ℃ is preferably 10 to 35.

When the relative dielectric constant of the polar solvent is less than 10 at 20 ℃, the affinity for water is low, and therefore, the reaction between the surface of the phosphor particles and water is less likely to occur, and the dispersibility of the fired product is undesirably lowered. When the relative dielectric constant of the polar solvent at 20 ℃ exceeds 70, the affinity for water is too high, and the decomposition of the fired product (phosphor) tends to occur due to the reaction with water, which is not preferable.

Examples of the polar solvent having a relative dielectric constant at 20 ℃ of 10 to 70 include: ethyl acetate, tetrahydrofuran, N-dimethylformamide, dimethyl sulfoxide, an alcohol having a linear or branched alkyl group having 1 to 8 carbon atoms, a carboxylic acid such as formic acid or acetic acid, or a ketone such as acetone. The polar solvent having a relative dielectric constant at 20 ℃ of 10 or more and 70 or less is preferably an alcohol and/or a ketone.

When an alcohol and/or a ketone is used as the polar solvent, a lower alcohol and/or a ketone having a linear or branched alkyl group having 1 to 4 carbon atoms is preferable. The polar solvent is more preferably at least 1 selected from methanol (relative dielectric constant 33), ethanol (relative dielectric constant 24), 1-propanol (relative dielectric constant 20), 2-propanol (relative dielectric constant 18), and acetone (relative dielectric constant 21). The polar solvent may be used alone in 1 kind, or 2 or more kinds may be used in combination.

In the production method of the present embodiment, the polar solvent may contain water having a relative dielectric constant of 80 at 20 ℃, and the content of water in the polar solvent which is an alcohol and/or a ketone may be 0.01 mass% or more and 12 mass% or less. The content of water in the polar solvent having a relative dielectric constant at 20 ℃ of 10 to 70 inclusive is preferably 0.01 to 12% by mass. The content of water in the polar solvent is more preferably 0.1 mass% or more and 10 mass% or less. In general, water is often used for dispersion of phosphor particles. The nitride phosphor containing the fired product having the composition of the formula (I) tends to be decomposed by reacting with water in the presence of more than a certain amount of water. In the production method of the present embodiment, by containing a certain amount of water in the polar solvent, it is possible to form a compound having a composition different from that of the nitride phosphor on at least a part of the particle surface of the fired product while suppressing decomposition of the fired product constituting the phosphor particles. It is considered that, by adjusting, for example, the refractive index in the vicinity of the surface of the phosphor particles, and by efficiently guiding light to the outside of the phosphor particles, the emission intensity of the phosphor can be improved.

In the production method of the present embodiment, the particles of the fired product are preferably stirred in a polar solvent. The particles of the fired product can be dispersed by stirring the fired product in a polar solvent. Since the dispersion of the particles of the fired product is promoted when the fired product is stirred in the polar solvent, a dispersion medium such as alumina balls or zirconia balls may be added. It is considered that by stirring the fired product in a polar solvent, the particles of the fired product are dispersed and at the same time, hydroxides or oxides are formed on at least a part of the particle surfaces. While polar solvents improve the emission characteristics of nitride phosphors, it is difficult to improve the emission characteristics in nonpolar solvents. This is presumably because, when water is contained in a polar solvent, for example, hydroxides or oxides can be formed on at least a part of the surface of the phosphor particles, whereas a nonpolar solvent has low affinity with water, and thus it is difficult to form hydroxides or oxides on the surface of the phosphor particles by water.

[ classifying step ]

The production method of the present embodiment may include a step of classifying the nitride phosphor to obtain a nitride phosphor having an average particle size of 4.0 μm or more after the step of mixing the fired product and the polar solvent. By the classifying step, the average particle diameter of the nitride phosphor can be made to be a predetermined value or more, and the nitride phosphor having further improved excitation light absorptance and emission intensity with respect to the nitride phosphor can be obtained. Specifically, the classification step is carried out by sieving, sedimentation and classification in a solution by gravity, centrifugal separation, or the like, to obtain a nitride phosphor having an average particle size of 4.0 μm or more. According to the production method of the present embodiment, it is preferable to obtain a nitride phosphor having an average particle size of 4.0 to 20 μm, more preferably 5.0 to 18 μm, through the classification step.

Specific examples of the nitride phosphor obtained by the production method of the present embodiment will be described later, but the nitride phosphor obtained by the production method of the present embodiment has a composition represented by formula (I). In the nitride phosphor obtained by the production method of the present embodiment, the content of the oxygen element in the nitride phosphor is 2 mass% or more and 4 mass% or less.

The oxygen element contained in the nitride phosphor may contain, in addition to the oxygen element contained in the hydroxide or oxide which is considered to be formed by mixing the fired product and the polar solvent, the oxygen element derived from the hydroxide or oxide which is formed on the particle surface by leaving the particles of the phosphor in the air. It is estimated that the amount of hydroxide and oxide generated by exposing the phosphor particles to the air is extremely small.

The nitride phosphor obtained by the production method of the present embodiment has the composition represented by formula (I) above, and may further contain a fluorine element. It is considered that fluorine contained in the nitride phosphor is derived from the raw material mixture and the flux.

(nitride phosphor)

The nitride phosphor according to the embodiment of the present invention contains a fired product having a composition represented by the following formula (I), and the content of an oxygen element is 2 mass% or more and 4 mass% or less.

M^a _vM^b _wM^c _xM^d _yN_z(I)

Here, in the formula (I), M^aIs at least 1 element selected from Sr, Ca, Ba and Mg, M^bIs at least 1 element selected from Li, Na and K, M^cIs selected from EuAt least 1 element of Mn, Tb and Ce, M^dIs at least 1 element selected from Al, Si, B, Ga, In, Ge and Sn, particularly preferably at least 1 element selected from Al, B, Ga and In, and v, w, x, y and z are numbers satisfying 0.8. ltoreq. v.ltoreq.1.1, 0.8. ltoreq. w.ltoreq.1.1, 0.001. ltoreq. x.ltoreq.0.1, 2.0. ltoreq. y.ltoreq.4.0, 3.0. ltoreq. z.ltoreq.5.0, respectively.

The nitride phosphor according to the present embodiment contains oxygen, although not described in the composition shown in formula (I). The oxygen element contained in the nitride phosphor of the present embodiment is considered to be mainly derived from the oxygen element of the hydroxide or oxide formed on at least a part of the surface when the particles of the fired product and the polar solvent are mixed. The oxygen element contained in the nitride phosphor of the present embodiment may also include oxygen elements derived from hydroxides or oxides formed on the particle surfaces, which are generated by leaving the phosphor particles in the air. The amount of hydroxide and oxide generated by exposing the phosphor particles to the atmosphere is very small. The oxygen element not contained in the phosphor having the composition represented by the above formula (I) may be derived from the following source. Oxygen elements from the following are sometimes included: (1) a trace amount of hydroxide or oxide contained in various nitrides, hydrides, metals, etc. of the raw material mixture, (2) an oxide produced by oxidation of the raw material mixture during heat treatment, and (3) oxygen elements as a deposit on the produced nitride phosphor. However, the content of oxygen element derived from the oxides or the deposits of the above (1) to (3) is extremely small. The content of oxygen elements derived from the oxides or attachments of the above (1) to (3) contained in the nitride phosphor of the present embodiment is an extremely small amount of less than 0.1 mass%.

In general, when oxygen is present in a nitride phosphor, the crystal structure of the phosphor can be changed by controlling the molar ratio of oxygen so as to shift the emission peak wavelength of the phosphor. On the other hand, from the viewpoint of high emission intensity, the nitride phosphor preferably contains less oxygen. It is considered that when the amount of oxygen contained in the nitride phosphor increases, the influence of oxygen not only stays on the surface of the phosphor particles but also reaches the inside, and the crystal structure of the nitride phosphor becomes unstable. When the crystal structure of the nitride phosphor becomes unstable, the emission intensity tends to decrease. Therefore, when the nitride phosphor contains oxygen, it is preferable that the oxygen element is contained in the vicinity of the surface of the nitride phosphor.

The content of the oxygen element in the nitride phosphor of the present embodiment is 2 mass% or more and 4 mass% or less. The content of the oxygen element in the nitride phosphor is preferably 2.2 mass% or more and 3.8 mass% or less, and more preferably 2.5 mass% or more and 3.5 mass% or less.

When the content of the oxygen element in the nitride phosphor exceeds 4 mass%, the content of oxygen increases, and oxygen not only stays on the surface of the phosphor particle but also reaches the inside, and the emission intensity tends to decrease. On the other hand, when the content of oxygen element in the nitride phosphor is less than 2 mass%, it is difficult to form a hydroxide or an oxide which can improve only light emitted to the outside of the phosphor particle in the vicinity of the surface of the phosphor particle, and it tends to be difficult to improve the emission intensity.

The nitride phosphor according to the present embodiment may further contain fluorine, and the content of fluorine is preferably 0.1 mass% or more and 1 mass% or less. The content of the fluorine element contained in the nitride phosphor is more preferably 0.2 mass% or more and 0.8 mass% or less, and still more preferably 0.3 mass% or more and 0.7 mass% or less. It is presumed that the fluorine element contained in the nitride phosphor is derived from the raw material mixture and the flux.

When the content of the fluorine element in the nitride phosphor is 0.1 mass% or more and 1 mass% or less, a part of the nitride phosphor is decomposed to reduce the possibility that another compound is present in the nitride phosphor, and a decrease in the emission intensity due to the presence of the other compound can be suppressed.

The nitride phosphor of the present embodiment preferably has an internal quantum efficiency of 80% or more, and more preferably has an internal quantum efficiency of 81% or more. This can improve the emission intensity of the nitride phosphor.

The nitride phosphor according to the present embodiment preferably has an external quantum efficiency of more than 55%, more preferably 56% or more. This can improve the emission intensity of the nitride phosphor.

In the formula (I), M is preferred from the viewpoint of improving the emission intensity^aComprises at least one of Ca and Sr. M^aWhen at least one of Ca and Sr is contained, M^aThe total molar ratio of Ca and Sr contained in (a) is, for example, 85 mol% or more, preferably 90 mol% or more.

In addition, in the formula (I), M is preferable from the viewpoint of stability of the crystal structure^bContaining at least Li. M^bIn the case of containing Li, M^bThe molar ratio of Li contained in (a) is, for example, 80 mol% or more, preferably 90 mol% or more.

Furthermore, in the formula (I), M is preferred^cIs Eu, M^dIs Al. In the formula (I), M^cIs Eu, M^dIn the case of Al, a nitride phosphor having a narrow half-value width of the emission spectrum and a desired wavelength range can be obtained.

There is no particular limitation as long as v, w, x, y and z in formula (I) satisfy the above numerical ranges, respectively. From the viewpoint of crystal structure stability, the numerical values of v and w are 0.8 or more and 1.1 or less, preferably 0.9 or more and 1.05 or less, respectively. x is an Eu activation amount, and may be appropriately selected so as to achieve desired characteristics. x is a number satisfying 0.001 < x.ltoreq.0.1, preferably 0.001 < x.ltoreq.0.02, more preferably 0.002. ltoreq.x.ltoreq.0.015. From the viewpoint of stability of the crystal structure, y is a number satisfying 2.0. ltoreq. y.ltoreq.4.0, preferably 2.0. ltoreq. y.ltoreq.3.5. Also, from the viewpoint of stability of the crystal structure, z is a number satisfying 3.0. ltoreq. z.ltoreq.5.0, preferably 3.0. ltoreq. z.ltoreq.4.0.

The nitride phosphor of the present embodiment may contain impurities not present in the composition of formula (I). The impurities which may be present in the nitride phosphor may be selected from Sc, Y, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Ru, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Hf, Ta, W, Re, Os, Ir, Pt, Tl, Pb and Bi.

The nitride phosphor according to the present embodiment absorbs light in a wavelength range of 400nm to 570nm inclusive, which is a short wavelength range from ultraviolet to visible light, and emits fluorescence having an emission peak wavelength in a wavelength range of 630nm to 670nm inclusive. By using an excitation light source in this wavelength range, a phosphor having high emission intensity can be provided. The excitation light source preferably has a main emission peak wavelength of 420nm or more and 500nm or less, and more preferably has a main emission peak wavelength of 420nm or more and 460nm or less.

The emission peak wavelength of the emission spectrum of the nitride phosphor is in the range of 630nm to 670nm, preferably 640nm to 660 nm. The half-value width of the emission spectrum is, for example, 65nm or less, preferably 60nm or less. The lower limit of the half-value width is, for example, 45nm or more.

Nitride phosphor M^cAt M as a luminescent center^cIn the case of europium (Eu) as a rare earth element, europium (Eu) serves as a luminescence center. However, the luminescence center of the present embodiment is not limited to europium, and europium in the luminescence center may be partially substituted with another rare earth metal element or alkaline earth metal element. The other elements and europium can be used as co-activators. Eu at 2-valent rare earth ion²⁺Light emission is stably performed by selecting an appropriate host crystal.

The average particle diameter of the nitride phosphor is, for example, 4.0 μm or more, preferably 4.5 μm or more, and more preferably 5.0 μm or more. The average particle diameter is, for example, 20 μm or less, preferably 18 μm or less.

When the average particle diameter is not less than a predetermined value, the excitation light absorptance and emission intensity of the nitride phosphor tend to be higher. In this way, by incorporating a nitride phosphor having excellent light emission characteristics into a light-emitting device described later, the light emission efficiency of the light-emitting device can be improved. Further, by setting the average particle diameter to a predetermined value or less, workability in the manufacturing process of the light-emitting device can be improved.

The nitride phosphor preferably contains phosphor particles having the above average particle diameter at a high frequency. That is, the nitride phosphor preferably has a narrow particle size distribution. By using nitride phosphor particles having small variations in particle size, color unevenness can be suppressed, and a light-emitting device having a good color tone can be obtained.

In the present specification, the average particle size of the nitride phosphor and the average particle size of the phosphors other than the nitride phosphor are volume average particle sizes, and are particle sizes (median particle sizes) that can be measured by a laser diffraction particle size distribution measuring apparatus (MASTER size r 2000, manufactured by MALVERN corporation).

The nitride phosphor preferably has a crystal structure in most of the particles. For example, since the glass body (amorphous) has a loose (lose) crystal structure, the ratio of the components in the phosphor is not constant, and there is a risk of occurrence of color unevenness and the like. Therefore, in order to avoid this, it is necessary to strictly manage the consistency of the reaction conditions in the production process. Most phosphors having a crystal structure are easy to manufacture and process. In addition, since the phosphor is easily uniformly dispersed in the resin, a sealing member described later can be easily formed. The content of the crystal structure in the phosphor particle indicates the proportion of the crystal phase having a light-emitting property. The nitride phosphor preferably has a crystal phase of at least 50 mass% or more, more preferably 80 mass% or more. When the crystal phase has a luminescent property of 50 mass% or more, practically durable luminescence can be obtained.

(light-emitting device)

Next, a light-emitting device using a nitride phosphor as a wavelength conversion member will be described. The light-emitting device according to the embodiment of the present invention includes the nitride phosphor and an excitation light source. The excitation light source is preferably a light source that emits light in a range of 400nm to 570 nm.

The excitation light source may use a light emitting element. The light-emitting element emits light in a wavelength range of 400nm to 570 nm. The light-emitting element preferably has an emission peak wavelength in a wavelength range of 420nm to 460 nm. By using a light-emitting element having an emission peak wavelength in this range as an excitation light source, a light-emitting device that emits a mixed color light of light from the light-emitting element and fluorescence from a phosphor can be configured. Since a part of light emitted from the light-emitting element to the outside can be effectively used as light of the light-emitting device, the light-emitting device with high light-emitting efficiency can be obtained.

As the light-emitting element, for example, a light-emitting element using a nitride semiconductor (In) is preferably used_XAl_YGa_1-X-YN, 0. ltoreq. X, 0. ltoreq. Y, X + Y. ltoreq.1) of a semiconductor light-emitting element emitting blue or green light. By using a semiconductor light emitting element as a light source, a light emitting device having high efficiency, high linearity of output with respect to input, and high and stable mechanical shock resistance can be obtained. The half-width of the emission spectrum of the light-emitting element may be 30nm or less, for example.

The first phosphor included in the light-emitting device contains the above-described nitride phosphor. The nitride phosphor has a composition represented by the above formula (I), can be excited by light having a wavelength range of 400nm to 570nm, and has an emission peak wavelength in a wavelength range of 630nm to 670 nm.

The first phosphor may be contained in a sealing resin covering the excitation light source, for example, to constitute a light emitting device. In a light-emitting device in which an excitation light source is covered with a sealing resin containing a first phosphor, a part of light emitted from the excitation light source is absorbed by the first phosphor and emitted as red light. By using an excitation light source that emits light in a wavelength range of 400nm to 570nm, the emitted light can be used more efficiently. This reduces the loss of light emitted from the light-emitting device, and provides a light-emitting device with high light-emitting efficiency.

The content of the first phosphor contained in the light-emitting device may be, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, per 100 parts by mass of the sealing resin.

The light-emitting device may include a second phosphor having a different emission peak wavelength range from the first phosphor. For example, the light-emitting device can have a wide color reproduction range or high color rendering properties by appropriately providing a light-emitting element that emits blue light and a first phosphor and a second phosphor that are excited by the light-emitting element.

The second phosphor preferably contains, for example: at least one phosphor having a composition represented by any one of the following formulae (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (IIg), (IIh) and (IIi). The second phosphor more preferably contains at least 1 kind of phosphor having a composition represented by formula (IIc), (IIe), (IIh), or (IIi), for example, from the viewpoint of obtaining a wide color reproduction range.

(Y,Gd,Tb,Lu)₃(Al,Ga)₅O₁₂:Ce (IIa)

(Ba,Sr,Ca)₂SiO₄:Eu (IIb)

Si_6-pAl_pO_pN_8-p:Eu(0＜p≤4.2) (IIc)

(Ca,Sr)₈MgSi₄O₁₆(Cl,F,Br)₂:Eu (IId)

(Ba,Sr,Ca)Ga₂S₄:Eu (IIe)

(Ba,Sr,Ca)₂Si₅N₈:Eu (IIf)

(Sr,Ca)AlSiN₃:Eu (IIg)

K₂(Si,Ge,Ti)F₆:Mn (IIh)

(Ba,Sr)MgAl₁₀O₁₇:Mn (IIi)

The average particle size of the second phosphor is preferably 2 μm or more and 35 μm or less, and more preferably 5 μm or more and 30 μm or less. By setting the average particle diameter to a predetermined value or less, workability in the manufacturing process of the light-emitting device can be improved.

The content of the second phosphor may be appropriately selected according to the purpose and the like. For example, the content of the second phosphor may be 1 to 200 parts by mass, preferably 2 to 180 parts by mass, based on 100 parts by mass of the sealing resin.

The content ratio of the first phosphor to the second phosphor, for example, the content ratio of the first phosphor to the second phosphor (first phosphor/second phosphor) may be 0.01 to 5, preferably 0.05 to 3, on a mass basis.

The first phosphor and the second phosphor (hereinafter, the first phosphor and the second phosphor are also collectively referred to simply as "phosphors") preferably constitute a sealing member that covers the light-emitting element together with a sealing resin. Examples of the sealing resin constituting the sealing member include epoxy resin and silicone resin.

The total content of the phosphor in the sealing member may be, for example, 5 to 300 parts by mass, preferably 10 to 250 parts by mass, more preferably 15 to 230 parts by mass, and still more preferably 15 to 200 parts by mass, based on 100 parts by mass of the sealing resin.

The sealing member may further contain a filler, a light diffusing material, and the like in addition to the sealing resin and the phosphor. Examples of the filler and the light diffusing material include: silica, titania, zinc oxide, zirconia, alumina, and the like. When the sealing member contains a filler, the content thereof may be appropriately selected depending on the purpose and the like. The content of the filler may be, for example, 1 to 20 parts by mass with respect to 100 parts by mass of the sealing resin.

An example of the light-emitting device of the present embodiment will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing an example of a light-emitting device according to the present embodiment.

The light-emitting device 100 includes: the light emitting device includes a package 40 having a recess, a light emitting element 10, and a sealing member 50 covering the light emitting element 10. The light emitting element 10 is disposed in a recess formed in the package 40, and is electrically connected to the pair of positive and negative lead electrodes 20 and 30 disposed in the package 40 via a conductive cable 60. The sealing member 50 is formed by filling a sealing resin containing a phosphor 70 in the concave portion, and covers the light emitting element 10. The sealing member 50 contains, for example, a phosphor 70 that wavelength-converts light from the sealing resin and the light emitting element 10. Further, the phosphor 70 includes a first phosphor 71 and a second phosphor 72. A part of the pair of positive and negative lead electrodes 20 and 30 is exposed to the outside of the package 40. The light-emitting device 100 receives power supply from the outside through the lead electrodes 20 and 30, and emits light.

The sealing member 50 functions not only as a wavelength conversion member but also as a member for protecting the light-emitting element 10, the first phosphor 71, and the second phosphor 72 from the external environment. In fig. 1, the first phosphor 71 and the second phosphor 72 are unevenly present in the sealing member 50. By disposing the first phosphor 71 and the first phosphor 72 close to the light-emitting element 10 in this way, light from the light-emitting element 10 can be efficiently wavelength-converted, and a light-emitting device with excellent light emission efficiency can be obtained. The arrangement of the sealing member 50 including the first fluorescent material 71 and the first fluorescent material 72 and the light-emitting element 10 is not limited to the arrangement close to these, and the light-emitting element 10 may be arranged in the sealing member 50 with a space between the first fluorescent material 71 and the first fluorescent material 72 in consideration of the influence of heat on the first fluorescent material 71 and the first fluorescent material 72. Further, by mixing the first phosphor 71 and the first phosphor 72 at a substantially uniform ratio in the entire sealing member 50, light in which color unevenness is further suppressed can be obtained.

Examples

The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Production example 1

To obtain a composition containing a compound having M^a _vM^b _wM^c _xM^d _yN_zA nitride phosphor of a fired product of the composition M^aIs Sr, M^bIs Li, M^cIs Eu, M^dIs Al, and SrN is used_u(corresponding to u-2/3, SrN)₂And SrN), SrF₂、LiAlH₄、AlN、EuF₃Raw materials were weighed and mixed in a glove box in an inert gas atmosphere so that the molar ratio of Sr to Li to Eu to Al was 0.9925:1.2:0.0075:3, thereby obtaining a raw material mixture. Here, SrN is made_uAnd SrF₂In a mass ratio of 94: 6. In addition, since Li is easily scattered during firing, it is blended slightly more than the value of the target composition. The raw material mixture was charged into a crucible, and heat-treated at 1100 ℃ for 3 hours in a nitrogen atmosphere at a gas pressure of 0.92MPa (1.02 MPa absolute) in gauge pressure for obtaining a powder of a fired product (phosphor) 1.

(example 1)

30g of the calcined product 1 obtained in production example 1 was added to 80ml of ethanol (purity: 99.5% or more, relative dielectric constant: 24 at 20 ℃ C., and water content: 0.03% by mass), and the mixture was stirred for 3 hours. After the stirring treatment, coarse particles and fine particles were removed by classification treatment, and further subjected to solid-liquid separation and drying, thereby obtaining nitride phosphors of example 1 having an average particle diameter (Dm) adjusted as shown in table 1.

Comparative example 1

The fired product 1 obtained in production example 1 was made into the nitride phosphor of comparative example 1.

(example 2)

A nitride phosphor of example 2 was obtained under the same conditions as in example 1 except that pure water was added so that the water content in ethanol became 1 mass%.

(example 3)

A nitride phosphor of example 3 was obtained under the same conditions as in example 1 except that pure water was added so that the water content in ethanol became 5 mass%.

(example 4)

A nitride phosphor of example 4 was obtained under the same conditions as in example 1 except that pure water was added so that the water content in ethanol became 10 mass%.

Comparative example 2

A nitride phosphor of comparative example 2 was obtained under the same conditions as in example 1, except that pure water was added so that the water content in ethanol became 12.5 mass%.

Comparative example 3

A nitride phosphor of comparative example 3 was obtained under the same conditions as in example 1, except that pure water was added so that the water content in ethanol became 15.0 mass%.

Comparative example 4

A nitride phosphor of comparative example 4 was obtained under the same conditions as in example 1, except that pure water was added so that the water content in ethanol became 17.5 mass%.

Comparative example 5

A nitride phosphor of comparative example 5 was obtained under the same conditions as in example 1, except that pure water was added so that the water content in ethanol was 20 mass%.

Comparative example 6

A nitride phosphor of comparative example 6 was obtained under the same conditions as in example 1, except that pure water was added so that the water content in ethanol became 50 mass%.

(example 5)

A nitride phosphor of example 5 was obtained under the same conditions as in example 1 except that ethanol was changed to 2-propanol (purity: 99.7% or more, relative permittivity at 20 ℃ 18, and water content: 0.11% by mass).

Comparative example 7

A nitride phosphor of comparative example 7 was obtained under the same conditions as in example 1, except that ethanol was changed to hexane (purity: 96% or more, relative permittivity 2 at 20 ℃, and water content: less than 0.01% by mass).

< evaluation >

(X-ray diffraction Pattern)

An X-ray diffraction pattern (XRD) was measured for the obtained nitride phosphor. The measurement was carried out by using CuK.alpha.rays using a sample horizontal type multi-functional X-ray diffraction apparatus (product name: UltimaIV, manufactured by Nippon chemical Co., Ltd.). An example of the XRD pattern obtained is shown in fig. 2.

(average particle diameter)

The average particle size of the obtained nitride phosphor was measured by a laser diffraction particle size distribution measuring apparatus (MASTER size 2000, manufactured by MALVERN corporation). The results are shown in Table 1.

(luminescent Property)

The luminescence characteristics of the obtained nitride phosphor were measured. The emission characteristics of the nitride phosphor powder were measured by using a fluorescence spectrophotometer QE-2000 (available from Otsuka electronics Co., Ltd.) with an excitation light wavelength of 450 nm. From the obtained emission spectrum, the relative emission intensity Ip (%), the emission peak wavelength λ p (nm), the internal quantum efficiency (%), and the external quantum efficiency (%) were obtained. The results are shown in Table 1. The relative emission intensity Ip (%) was calculated based on the nitride phosphor of comparative example 1.

Fig. 3 shows emission spectra of the nitride phosphors obtained in comparative example 1 and example 1. The emission spectrum of fig. 3 shows relative emission intensity with respect to wavelength.

(composition analysis)

The composition ratios (molar ratios) of the respective elements Sr, Li, Eu, Al and N were determined by ICP emission spectrometry using an inductively coupled plasma emission spectrometer (PerkinElmer). The content (mass%) of O, F in the obtained nitride phosphor was measured by an oxygen/nitrogen analyzer manufactured by horiba ltd. The results are shown in Table 2. The composition ratio (molar ratio) of each element was determined based on the composition ratio (molar ratio) of Al being 3.

(SEM photograph)

SEM images of the nitride phosphors of examples 1 and 4 and comparative example 6 were obtained using a Scanning Electron Microscope (SEM). Fig. 4 is an SEM photograph of the nitride phosphor of example 1, fig. 5 is an SEM photograph of the nitride phosphor of example 4, and fig. 6 is an SEM photograph of the nitride phosphor of comparative example 6.

[ Table 1]

[ Table 2]

As is clear from the relative emission intensities shown in Table 1, the relative emission intensities of examples 1 to 5 are all higher than those of comparative example 1. Further, as is clear from the emission spectrum shown in fig. 3, the relative emission intensity of example 1 is higher than that of comparative example 1. As shown in Table 1, the internal quantum efficiencies of examples 1 to 5 were all 80% or more, which were higher than those of comparative examples 1 and 5 to 7. In addition, the external quantum efficiencies of examples 1 to 5 were all 58% or more, which was higher than that of comparative example. Thus, the light conversion efficiency of examples 1 to 5 was improved, and by using them as a phosphor constituting a light emitting device, a light emitting device capable of obtaining a larger luminous flux was obtained. Comparative examples 2 to 4 using a polar solvent having a water content of more than 12 mass% had external quantum efficiencies of 55% or less and also had low relative emission intensities. As shown in comparative examples 5 to 6, it is presumed that when the content of water in the polar solvent is 20 mass% or more, the decomposition of the water-based phosphor particles is promoted, the internal quantum efficiency is less than 80%, the external quantum efficiency is also 55% or less, and both the light conversion efficiency and the relative light emission intensity are lowered.

FIG. 2 shows comparative example 1, comparative example 5, comparative example 6, comparative example 7, example 1, example 4, example 5, and Sr for reference in that order from the top₃Al₂(OH)₁₂、LiAl₂(OH)₇·2H₂O、SrLiAl₃N₄XRD pattern of the compound (SLAN) shown.

As shown in FIG. 2, the compounds of comparative examples 1 and 5 to 7 and examples 1, 4 and 5 had the same XRD pattern as SLAN, and it was confirmed that they all had a composition of SrLiAl₃N₄The compound shown in the specification. Comparative examples 5 and 6 were conducted except that SrLiAl₃N₄In addition to Sr₃Al₂(OH)₁₂、LiAl₂(OH)₇·2H₂The peak of O or the like is considered to be that part of the phosphor particles are decomposed. As shown in FIG. 2, it is considered that comparative examples 5 and 6 are different from SrLiAl₃N₄In addition, since a small amount of other compounds is present, a part of the target compound is decomposed, and the relative emission intensity and internal quantum efficiency are reduced. Comparative example 7 is an example in which hexane having a relative dielectric constant of 2 at 20 ℃ was used instead of ethanol. Comparative example 7 did not have a relative emission intensity as high as examples 1 to 5, and the internal quantum efficiency was about the same as that of the other comparative examples, and no improvement in the emission characteristics was observed.

The composition ratios (molar ratios) of Sr, Eu, Li, and N shown in table 2 were determined based on the composition ratio (molar ratio) of Al being 3. The O (oxygen) element and the F (fluorine) element are expressed by mass ratio (% by mass). The elemental oxygen (O) in examples 1 to 5 was increased to 2 to 4% by mass as compared with comparative example 1. It is considered that by dispersing the fired product particles in a polar solvent having a relative dielectric constant of 10 or more and 70 or less at 20 ℃, the specific surface area of the particles in contact with the polar solvent is increased, and the surface of the particles is more strongly affected by the polar solvent, whereby the content of oxygen element in the phosphor particles is increased. In examples 1 to 5, the composition ratio (molar ratio) of Eu was not changed substantially with respect to the charged amount, and the composition ratio (molar ratio) of Sr and Li was slightly changed with respect to the charged amount. Although Li is considered to be significantly reduced in the heat treatment stage relative to the charged amount, it is understood that the composition ratio (molar ratio) of Li in the phosphor is not substantially changed in the solvent treatment with the polar solvent. In comparative examples 2 to 6, the fired product particles were dispersed in a polar solvent having a large water content, and the nitride phosphor particles were partially decomposed as described in the X-ray diffraction pattern (XRD), so that fluorine (F) element contained in the fired product was reacted with an excessive amount of water in the polar solvent to remove the fluorine element, and thus the content of fluorine (F) element was reduced as compared with comparative example 1.

The SEM photographs of the nitride phosphor of example 1 shown in fig. 4 and the SEM photograph of the nitride phosphor of example 4 shown in fig. 5 were not visually confirmed to be significantly different. On the other hand, in the SEM photograph of the nitride phosphor of comparative example 6 shown in fig. 6, it was confirmed that the surface of the nitride phosphor was rough. The surfaces of the nitride phosphor of example 1 and the nitride phosphor of example 4 were smooth as compared with the SEM photographs of fig. 4 and 5, but the nitride phosphor of comparative example 6 of fig. 6 was estimated to have rough surfaces due to the partial decomposition of the nitride phosphor.

Since the nitride phosphor of the present embodiment has excellent emission intensity, a light-emitting device with a large light beam can be provided by using the nitride phosphor.

Industrial applicability

The light-emitting device using the nitride phosphor according to the present disclosure can be suitably used as a light source for illumination or the like. In particular, the present invention can be suitably used as an illumination light source, an LED display, a liquid crystal backlight, a traffic light, an illumination switch, various sensors, various indicators, and the like, which have extremely excellent light emission characteristics using a light emitting diode as an excitation light source.

Claims

1. A method for producing a nitride phosphor containing a fired product having a composition represented by the following formula (I) and having an oxygen element content of 2 to 4 mass%,

M^a _vM^b _wM^c _xM^d _yN_z(I)

in the formula (I), the compound is shown in the specification,

M^ais at least 1 element selected from Sr, Ca, Ba and Mg,

M^bis selected fromAt least 1 element selected from Li, Na and K,

M^cis at least 1 element selected from Eu, Mn, Tb and Ce,

M^dis at least 1 element selected from Al, B, Ga and In,

v, w, x, y and z are numbers satisfying 0.8. ltoreq. v.ltoreq.1.1, 0.8. ltoreq. w.ltoreq.1.1, 0.001. ltoreq. x.ltoreq.0.1, 2.0. ltoreq. y.ltoreq.4.0, 3.0. ltoreq. z.ltoreq.5.0,

the manufacturing method comprises the following steps:

a step of preparing a fired product having a composition represented by the formula (I) and mixing the fired product with a polar solvent having a relative dielectric constant at 20 ℃ of 10 to 70 inclusive.

2. A method for manufacturing a nitride phosphor, comprising:

a step of preparing a fired product having a composition represented by the following formula (I), and mixing the fired product with a polar solvent,

the polar solvent is an alcohol and/or a ketone containing 0.01 to 12 mass% of water,

M^a _vM^b _wM^c _xM^d _yN_z(I)

in the formula (I), the compound is shown in the specification,

M^ais at least 1 element selected from Sr, Ca, Ba and Mg,

M^bis at least 1 element selected from Li, Na and K,

M^cis at least 1 element selected from Eu, Mn, Tb and Ce,

M^dis at least 1 element selected from Al, B, Ga and In,

v, w, x, y and z are numbers satisfying 0.8. ltoreq. v.ltoreq.1.1, 0.8. ltoreq. w.ltoreq.1.1, 0.001. ltoreq. x.ltoreq.0.1, 2.0. ltoreq. y.ltoreq.4.0, and 3.0. ltoreq. z.ltoreq.5.0, respectively.

3. The method for producing a nitride phosphor according to claim 1, wherein the polar solvent further contains water, and the content of water in the polar solvent is 0.01 mass% or more and 12 mass% or less.

4. The method for producing a nitride phosphor according to claim 2 or 3, wherein the content of water in the polar solvent is 0.1 mass% or more and 10 mass% or less.

5. The method for producing a nitride phosphor according to any one of claims 1 to 4, wherein the polar solvent has a relative dielectric constant of 10 or more and 35 or less at 20 ℃.

6. The method for producing a nitride phosphor according to any one of claims 1 and 3 to 5, wherein the polar solvent is an alcohol and/or a ketone.

7. The method for producing a nitride phosphor according to any one of claims 1 to 6, wherein the polar solvent is at least 1 selected from methanol, ethanol, 1-propanol, 2-propanol, and acetone.

8. The method for producing a nitride phosphor according to any one of claims 1 to 7, comprising a step of classifying the fired product to obtain a nitride phosphor having an average particle size of 4.0 μm or more after the step.

9. The method for producing a nitride phosphor according to any one of claims 1 to 8, wherein in the formula (I),

M^acomprises at least one of Sr and Ca,

M^bthe lithium-containing material contains Li in an amount of,

M^cis Eu as the raw material,

M^dis Al.

10. A nitride phosphor comprising a fired product having a composition represented by the following formula (I) and having an oxygen element content of 2 to 4 mass%,

M^a _vM^b _wM^c _xM^d _yN_z(I)

in the formula (I), the compound is shown in the specification,

M^ais at least 1 element selected from Sr, Ca, Ba and Mg,

M^bis at least 1 element selected from Li, Na and K,

M^cis at least 1 element selected from Eu, Mn, Tb and Ce,

M^dis at least 1 element selected from Al, B, Ga and In,

11. The nitride phosphor according to claim 10, wherein the content of fluorine element is 0.1 mass% or more and 1 mass% or less.

12. The nitride phosphor according to claim 10 or 11, wherein the internal quantum efficiency is 80% or more.

13. The nitride phosphor according to any one of claims 10 to 12, wherein, in the formula (I),

M^acomprises at least one of Sr and Ca,

M^bthe lithium-containing material contains Li in an amount of,

M^cis Eu as the raw material,

M^dis Al.

14. A light-emitting device is provided with:

the nitride phosphor according to any one of claims 10 to 13, and

an excitation light source.

15. The light-emitting device according to claim 14, comprising a second phosphor having an emission peak wavelength different from that of the nitride phosphor, the second phosphor containing at least 1 kind of phosphor selected from the group consisting of phosphors represented by the following formulae:

Si_6-pAl_pO_pN_8-p:Eu(0＜p≤4.2)

(Ca,Sr)₈MgSi₄O₁₆(Cl,F,Br)₂:Eu

(Ba,Sr,Ca)Ga₂S₄:Eu

(Ba,Sr)MgAl₁₀O₁₇:Mn

(Sr,Ca)AlSiN₃eu and

K₂(Si,Ge,Ti)F₆:Mn。