Method for producing nitride phosphor and nitride phosphor

Abstract

To provide a method for producing nitride phosphor having excellent durability, and nitride phosphor.SOLUTION: A method for producing nitride phosphor includes: preparing phosphor core particles which have a composition containing Sr, Ca, Eu, Al, Si and N, when a molar ratio in the composition of Al is 1, the molar ratio of Sr is within the range of 0.45 or more and 1.1 or less, the molar ratio of Ca is within the range of more than 0 and less than 0.55, the molar ratio of Eu is within the range of more than 0 and 0.033 or less, the molar ratio of the total of Sr, Ca and Eu is 1.1 or less, the molar ratio of Si is within the range of 0.81 or more and 1.21 or less, the molar ratio of N is within the range of 2.25 or more and 3.85 or less; bringing urea, silicate, water and the phosphor core particles into contact with one another, and performing first heating treatment within the range of the temperature of 70°C or higher and 150°C or lower; and performing second heating treatment to phosphor core particles, to which the first heating treatment has been performed, within the range of the temperature of 350°C or higher and 600°C or lower.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a nitride phosphor and to a nitride phosphor. [Background technology]

[0002] Light-emitting devices that combine light-emitting diodes (hereinafter also referred to as "LEDs") or laser diodes (hereinafter also referred to as "LDs") with phosphors are being widely used in lighting devices, backlights for liquid crystal display devices, etc., and are becoming increasingly widespread. One known nitride phosphor used in light-emitting devices is (Sr,Ca)AlSiN3:Eu, as disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 001860 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for further improvement in the durability of nitride phosphors. Therefore, an object of one aspect of the present invention is to obtain a nitride phosphor having excellent durability. [Means for solving the problem]

[0005] The present invention includes the following aspects. A first aspect of the present invention is a method for producing a nitride phosphor, comprising: preparing phosphor core particles having a composition containing Sr, Ca, Eu, Al, Si, and N, wherein, when the molar ratio of Al in the composition is taken as 1, the molar ratio of Sr is within a range of 0.45 to 1.1, the molar ratio of Ca is within a range of more than 0 but less than 0.55, the molar ratio of Eu is within a range of more than 0 but not more than 0.033, the molar ratio of the sum of Sr, Ca, and Eu is 1.1 or less, the molar ratio of Si is within a range of more than 0.81 but not more than 1.21, and the molar ratio of N is within a range of more than 2.25 but not more than 3.85; contacting the phosphor core particles with urea, silicate, and water, and performing a first heat treatment at a temperature within a range of more than 70°C but not more than 150°C; and performing a second heat treatment on the phosphor core particles that have been subjected to the first heat treatment at a temperature within a range of more than 350°C but not more than 600°C.

[0006] A second aspect of the present invention is a nitride phosphor comprising: a phosphor core particle having a composition containing Sr, Ca, Eu, Si, Al, and N, wherein, when the molar ratio of Al in the composition is taken as 1, the molar ratio of Sr is within the range of 0.45 or more and 1.1 or less, the molar ratio of Ca is within the range of more than 0 and less than 0.55, the molar ratio of Eu is within the range of more than 0 and 0.033 or less, the molar ratio of the sum of Sr, Ca, and Eu is 1.1 or less, the molar ratio of Si is within the range of more than 0.81 and 1.21, and the molar ratio of N is within the range of more than 2.25 and 3.85; and a first film on the surface of the phosphor core particle, which is provided, in this order from the phosphor core particle side, containing at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al, and oxygen, and a second film containing at least Si. [Effects of the Invention]

[0007] According to one aspect of the present invention, a nitride phosphor having excellent durability can be obtained. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a flowchart of a method for producing a nitride phosphor. [Figure 2] FIG. 2 is a flowchart of a method for producing a nitride phosphor. [Figure 3] FIG. 3 is a diagram showing the emission spectra of the nitride phosphors according to Example 1 and Comparative Example 1. As shown in FIG. [Figure 4] FIG. 4 is an SEM photograph of a backscattered electron image in which a part of the cross section of a particle of the nitride phosphor according to Example 1 is enlarged. [Figure 5] FIG. 5 is an SEM photograph of a secondary electron image of the nitride phosphor according to Example 1. As shown in FIG. [Figure 6] FIG. 6 is an SEM photograph of a secondary electron image of the nitride phosphor according to Comparative Example 1. As shown in FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an example of a light emitting device including a nitride phosphor. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a method for manufacturing a nitride phosphor and a nitride phosphor according to the present disclosure will be described based on embodiments. However, the embodiments shown below are merely examples for embodying the technical concept of the present invention, and the present invention is not limited to the method for manufacturing a nitride phosphor and the nitride phosphor described below. Note that in this specification, the relationship between color names and chromaticity coordinates, the relationship between light wavelength ranges and color names of monochromatic light, etc., conforms to JIS Z8110.

[0010] Method for manufacturing nitride phosphor A method for producing a nitride phosphor includes preparing phosphor core particles having a composition containing Sr, Ca, Eu, Al, Si, and N, wherein, when the molar ratio of Al in the composition is taken as 1, the molar ratio of Sr is within a range of 0.45 to 1.1, the molar ratio of Ca is within a range of more than 0 but less than 0.55, the molar ratio of Eu is within a range of more than 0 but not more than 0.033, the molar ratio of the sum of Sr, Ca, and Eu is 1.1 or less, the molar ratio of Si is within a range of more than 0.81 but not more than 1.21, and the molar ratio of N is within a range of more than 2.25 but not more than 3.85; contacting the phosphor core particles with urea, silicate, and water, and performing a first heat treatment at a temperature within a range of more than 70°C but not more than 150°C; and performing a second heat treatment on the phosphor core particles that have been subjected to the first heat treatment at a temperature within a range of more than 350°C but not more than 600°C.

[0011] 1 and 2 are flowcharts showing an example of the process sequence of a method for producing a nitride phosphor. The steps of the method for producing a nitride phosphor will be described with reference to the drawings. As shown in FIG. 1, the method for producing a nitride phosphor includes a phosphor core particle preparation step S101, a first heat treatment step S103 in which urea, silicate, water, and the phosphor core particles are brought into contact with each other and subjected to a first heat treatment at a temperature in the range of 70°C to 150°C, and a second heat treatment step S104 in which the phosphor core particles that have undergone the first heat treatment are subjected to a second heat treatment at a temperature in the range of 350°C to 600°C. As shown in FIG. 2, the method for producing a nitride phosphor may include a pre-heat treatment step S102 in which the phosphor core particles are brought into contact with water and subjected to a pre-heat treatment at a temperature in the range of 70°C to 150°C, prior to the first heat treatment step S103.

[0012] Preparation of phosphor core particles The phosphor core particle has a composition containing Sr, Ca, Eu, Al, Si, and N, and when the molar ratio of Al in the composition is 1, the molar ratio of Sr is in the range of 0.45 or more and 1.1 or less, the molar ratio of Ca is in the range of more than 0 and less than 0.55, the molar ratio of Eu is in the range of more than 0 and 0.033 or less, the molar ratio of the sum of Sr, Ca, and Eu is 1.1 or less, the molar ratio of Si is in the range of 0.81 or more and 1.21 or less, and the molar ratio of N is in the range of 2.25 or more and 3.85 or less.

[0013] Eu contained in the composition of the phosphor core particle is an activator element, and when the molar ratio of Al in the composition of the phosphor core particle is taken as 1, in order to obtain high luminescence intensity, the molar ratio of Eu is more preferably in the range of 0.0001 or more and 0.033 or less, and even more preferably in the range of 0.001 or more and 0.0275 or less. Ca is an element that constitutes the host crystal of the phosphor core particle together with Sr, Al, Si, and N. In order to obtain a stable crystal structure and desired chromaticity, when the molar ratio of Al in the composition of the phosphor core particle is taken as 1, the molar ratio of Ca is preferably in the range of 0.001 or more and less than 0.55, and more preferably in the range of 0.005 or more and less than 0.55.

[0014] The phosphor core particles preferably have a composition represented by the following formula (I). Sr u Ca v Eu w Si x Al y N z (I) (In the formula (I), u, v, w, x, y, and z are numbers satisfying 0.5 ≦ u ≦ 1.0, 0 < v < 0.5, 0 < w ≦ 0.03, u + v + w ≦ 1.0, 0.9 ≦ x ≦ 1.1, 0.9 ≦ y ≦ 1.1, and 2.5 ≦ z ≦ 3.5, respectively.)

[0015] The phosphor core particles can be obtained by heat-treating a raw material mixture prepared by mixing raw materials serving as Sr source, Ca source, Eu source, Si source, Al source, and N source so that the molar ratios of the respective elements in the composition constituting the phosphor core are within the above-mentioned ranges.

[0016] As the raw materials, compounds containing at least one element selected from the group consisting of Sr, Ca, Eu, Si, Al, and N included in the composition of the phosphor core particles can be used. Metals of Sr, Ca, Eu, Si, or Al may also be used. Examples of the compounds containing at least one element selected from the group consisting of Sr, Ca, Eu, Si, Al, and N included in the composition of the phosphor core particles include nitrides, hydrides, oxynitrides, oxides, hydroxides, fluorides, chlorides, amide compounds, or imide compounds. Since the amount of impurities contained in the obtained phosphor core particles can be reduced, it is preferable to use nitrides. Specifically, examples of the raw materials include Sr2N, SrN, Sr3N2, SrF2, SrH2, Ca3N2, CaF2, CaH2, EuN, EuF3, EuH3, Si3N4, Si(NH)2, Si2N2NH, Si(NH2)4, AlN, AlH3, AlF3, and LiAlH4.

[0017] The raw material mixture may be obtained by dry-mixing the raw materials using a ball mill, Henschel mixer, V-type blender, mortar, and pestle, or may be obtained by wet-mixing by adding a solvent or the like to the raw materials.

[0018] The raw material mixture may contain a flux. Examples of the flux include alkaline earth metal halides. The flux may be added as part of the raw materials for the phosphor core particles by adjusting the element ratio of cations contained in the flux to achieve the composition of the resulting phosphor core particles, or the flux may be added as an additional additive after adding the raw materials so as to achieve the desired composition of the phosphor core particles.

[0019] The temperature at which the raw material mixture is heat-treated is, for example, 1200°C or higher, preferably 1500°C or higher, and more preferably 1900°C or higher. The temperature at which the raw material mixture is heat-treated is, for example, 2200°C or lower, preferably 2100°C or lower, and more preferably 2050°C or lower. By heat-treating the raw material mixture at a temperature equal to or higher than a predetermined value, Eu can easily be incorporated into the crystal structure of the phosphor core particles, and phosphor core particles having the desired luminescence properties can be efficiently formed. Furthermore, when the temperature at which the raw material mixture is heat-treated is equal to or lower than a predetermined temperature, decomposition of the formed phosphor core particles is suppressed.

[0020] The heat treatment of the raw material mixture may be performed at a constant temperature, or may be performed in multiple stages with multiple heat treatment temperatures set. When performing heat treatment in multiple stages, the first stage may be performed at, for example, 800°C or higher and 1400°C or lower, and then the temperature may be gradually increased to 1500°C or higher and 2100°C or lower to perform the second stage. The temperature rise time of the heat treatment may be, for example, 1 hour or higher and 48 hours or lower. The temperature drop time of the heat treatment may be, for example, 0.1 hour or higher and 20 hours or lower. The heat treatment of the raw material mixture may include a holding time at a predetermined temperature. The holding time may be, for example, 0.5 hours or higher and 48 hours or lower.

[0021] The atmosphere in which the raw material mixture is heat-treated is preferably an atmosphere containing nitrogen gas, and more preferably an atmosphere containing substantially only nitrogen gas. When the heat-treatment atmosphere is an atmosphere containing nitrogen gas, decomposition of the raw material nitride or the phosphor core particles generated by the heat treatment can also be suppressed. When the heat-treatment atmosphere is an atmosphere containing nitrogen gas, in addition to nitrogen gas, it may contain other gases such as rare gases such as argon, neon, and helium, hydrogen, carbon dioxide, carbon monoxide, oxygen, and ammonia. When the heat-treatment atmosphere is an atmosphere containing nitrogen gas, the content of nitrogen gas in the atmosphere is, for example, 90% by volume or more, preferably 95% by volume or more. By setting the content of gases containing elements other than nitrogen to a predetermined value or less, a decrease in the luminescence intensity of the phosphor caused by impurities formed by these gas components is suppressed.

[0022] The pressure for the heat treatment of the raw material mixture can be, for example, normal pressure to 200 MPa (gauge pressure). From the viewpoint of suppressing decomposition of the nitride phosphor produced, a higher pressure is preferable, and a pressure of 0.1 MPa to 200 MPa is preferable, and a pressure of 0.6 MPa to 1.2 MPa is more preferable because it has fewer restrictions on industrial equipment.

[0023] The heat treatment of the raw material mixture can be carried out, for example, using a gas pressurized electric furnace. The heat treatment of the raw material mixture can be carried out, for example, by filling the raw material mixture into a crucible, boat, or the like made of a carbon material such as graphite or a boron nitride (BN) material. The crucible or boat into which the raw material mixture is filled may be made of alumina (Al2O3) or molybdenum (Mo). Of these, it is preferable to use a crucible or boat made of boron nitride.

[0024] The fired product obtained by heat-treating the raw material mixture may be subjected to sizing by combining processes such as crushing, grinding, and classification. Phosphor core particles having a desired particle size can be obtained by the sizing process. Specifically, the fired product obtained is roughly ground, and then ground to a predetermined particle size using a general grinder such as a ball mill, jet mill, or vibration mill. If particles with different particle sizes exist after grinding, classification may be performed to obtain phosphor core particles of the desired particle size. The fired product before or after classification may be washed by contacting it with deionized water, an acidic solution, or a basic solution to remove pyrolysis products adhering to the surface of the fired product.

[0025] Specifically, for example, by heat-treating a raw material mixture in which compounds containing each element are mixed to have a composition ratio of Sr:Ca:Eu:Al:Si=0.937:0.049:0.014:1.0:1.0, phosphor core particles having a composition in which the content ratio of Sr, Ca, Eu, Al, and Si reflects the charged composition ratio of each element can be obtained. Note that the phosphor core particles obtained by heat-treating the raw material mixture may contain oxygen components contained in the raw materials, or elements contained in the raw materials may be decomposed or dispersed during the heat treatment, resulting in a composition ratio slightly different from the charged composition ratio. Furthermore, the composition of the target phosphor core particles can be changed by changing the blending ratio of each raw material.

[0026] First heat treatment The obtained phosphor core particles are brought into contact with urea, silicate, and water, and subjected to a first heat treatment at a temperature in the range of 70°C to 150°C. By contacting the phosphor core particle with water and heat-treating it at a temperature range of 70°C or higher and 150°C or lower, a first film containing oxygen and at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al, which are constituent elements of the phosphor core particle, is formed on the surface of the phosphor core particle. The phosphor core particles, urea, silicate, and water are brought into contact with each other and subjected to a first heat treatment at a temperature ranging from 70°C to 150°C. This causes the urea and silicate to react with each other, hydrolyzing the urea and producing silicon dioxide, ammonia, and carbonate, forming a second film containing at least Si on the surface of the first film. The second film may contain silicon dioxide (SiO2) produced by the reaction of urea and silicate, and may also contain other elements besides Si, such as Al, in addition to Si. The first and second films formed on the surface of the phosphor core particles from the phosphor core particle side function as protective films against the external environment, protecting the phosphor core from, for example, moisture in the air.

[0027] Pre-heat treatment Before the first heat treatment, the phosphor core particles may be brought into contact with water and subjected to a pre-heat treatment at a temperature in the range of 70°C to 150°C. By performing the pre-heat treatment before the first heat treatment, a first film containing oxygen and at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al, which are constituent elements of the phosphor core particles, is formed. By performing the pre-heat treatment, the thickness of the first film containing oxygen and at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al, which are constituent elements of the phosphor core particles, (hereinafter also referred to as "film thickness of the first film") can be increased, and a protective film that protects the phosphor core particles from external influences such as high temperature and high humidity can be formed.

[0028] If the temperature of the first heat treatment or pre-heat treatment is within the range of 70°C or higher and 150°C or lower, the surface of the phosphor core particle reacts relatively slowly with water, and the elements constituting the phosphor core particle bond via oxygen, forming a first film with a stable structure and a substantially uniform thickness. The temperature of the first heat treatment or pre-heat treatment is preferably within the range of 80°C or higher and 140°C or lower, and more preferably within the range of 90°C or higher and 130°C or lower, in order to form a first film with a more stable structure in which the elements constituting the phosphor core particle are bonded to oxygen. If the temperature of the first heat treatment is within the range of 70°C or higher and 150°C or lower, silicon dioxide is produced by the reaction of urea with silicate, and the thickness of the second film (hereinafter also referred to as the "thickness of the second film") can be increased.

[0029] The treatment time of the first heat treatment or pre-heat treatment is preferably from 1 hour to 24 hours, more preferably from 2 hours to 20 hours, and even more preferably from 3 hours to 18 hours. When the treatment time of the first heat treatment or pre-heat treatment is from 1 hour to 24 hours, the first heat treatment or pre-heat treatment causes a relatively slow reaction between the surface of the phosphor core particle and water, and the elements constituting the phosphor core particle are bonded via oxygen to produce a first film with a stable structure, and furthermore, a second film containing at least Si is formed by the reaction of urea with silicate.

[0030] In the first heat treatment, the amount of silicate is preferably 2% by mass or more and 5% by mass or less relative to 100% by mass of the phosphor core particles. By reacting urea, silicate, water, and phosphor core particles in an amount of silicate within the range of 2% by mass or more and 5% by mass or less relative to 100% by mass of the phosphor core particles, a second film having a thickness sufficient to function as a protective film can be formed. Examples of silicate include alkali metal silicates and alkaline earth metal silicates, such as potassium or sodium metasilicic acid salts, with compositional formulas such as K2SiO3 and Na2SiO3. The mixing ratio of urea to silicate (urea:silicate) may be in the range of 1:10 to 10:1, 1:5 to 5:1, 1:3 to 3:1, or even 1:1, in terms of molar ratio. The amount of water in the first heat treatment or pre-heat treatment is not particularly limited. The amount of water in the pre-heat treatment or first heat treatment may be in the range of 50% by volume or more and 500% by volume or less relative to 100% by volume of the phosphor core particles, so that a first film and / or a second film having a uniform thickness and a stable structure is formed.

[0031] When the phosphor core particles are pre-heat-treated, the silicate content in the first heat treatment is preferably in the range of 2% to 5% by mass relative to 100% of the pre-heat-treated phosphor core particles. Even when the pre-heat treatment is performed, a second film containing at least Si and having a thickness sufficient to function as a protective film can be formed by reacting urea, silicate, water, and the phosphor core particles in an amount of silicate in the range of 2% to 5% by mass relative to 100% of the pre-heat-treated phosphor core particles. Even when the phosphor core particles are pre-heat-treated, the mixing ratio of urea to silicate (urea:silicate) (molar ratio) can be set within the same range as described above.

[0032] The atmosphere for the pre-heat treatment or the first heat treatment may be an oxygen-containing atmosphere or an air atmosphere, and the pressure for the pre-heat treatment or the first heat treatment may be atmospheric pressure.

[0033] After the first heat treatment and before the second heat treatment, the phosphor core particles that have been subjected to the first heat treatment may be washed with, for example, deionized water and filtered to remove any remaining urea or silicate, and the phosphor core particles may be separated from the water. In addition, a drying treatment may be performed after the washing.

[0034] The phosphor core particles that have been subjected to the pre-heat treatment or the first heat treatment may be subjected to a drying treatment after the pre-heat treatment but before the first heat treatment, or after the first heat treatment but before the second heat treatment. The temperature of the drying treatment is preferably lower than the temperature of the pre-heat treatment or the first heat treatment. Specifically, the temperature of the drying treatment is preferably in the range of 80°C or higher and 120°C or lower, and is preferably lower than the temperature of the pre-heat treatment or the first heat treatment. The drying time can be, for example, 1 hour or higher and 24 hours or lower. The drying treatment may be performed after the above-mentioned cleaning treatment.

[0035] Second heat treatment The phosphor core particles subjected to the first heat treatment are subjected to a second heat treatment at a temperature in the range of 350°C to 600°C. By further subjecting the phosphor core particles, on which a first film and a second film have been formed in that order from the phosphor core particle side by the first heat treatment, to a second heat treatment, impurities such as urea remaining in the first film and the second film can be removed. Furthermore, by subjecting the phosphor core particles after the first heat treatment to a second heat treatment, the density of the first film and the second film formed by the first heat treatment can be increased, further improving their function as protective films. The nitride phosphor obtained after the second heat treatment is protected by the double film of the first film and the second film, the density of which has been increased by the second heat treatment, making it less susceptible to the effects of moisture and carbon dioxide present in the external environment. This suppresses changes in chromaticity due to changes in composition, and improves durability.

[0036] The temperature of the second heat treatment is 350°C or higher and 600°C or lower, and preferably 400°C or higher and 550°C or lower in order to increase the density of the first film and the second film without causing defects in the crystal structure of the phosphor core particles.

[0037] The treatment time of the second heat treatment is preferably 3 hours to 24 hours, more preferably 4 hours to 20 hours, and even more preferably 5 hours to 18 hours. When the treatment time of the second heat treatment is 3 hours to 24 hours, the second heat treatment can increase the density of the first film and the second film and can remove impurities such as urea remaining during the first heat treatment.

[0038] The atmosphere for the second heat treatment may be an oxygen-containing atmosphere or an air atmosphere, since the first heat treatment forms a double protective film of the first film and the second film on the surface of the phosphor core particle. The pressure for the second heat treatment may be atmospheric pressure.

[0039] The second heat treatment can be carried out using, for example, a gas pressure electric furnace. The second heat treatment can be carried out by filling a crucible or boat made of the same material as that used for the heat treatment of the raw material mixture described above. In the second heat treatment, the crucible or boat into which the phosphor core particles on which the first and second films have been formed may be made of alumina (Al2O3) or molybdenum (Mo). Of these, it is preferable to use a crucible or boat made of boron nitride.

[0040] nitride phosphor The nitride phosphor has a composition containing Sr, Ca, Eu, Si, Al, and N, and when the molar ratio of Al in the composition is taken as 1, the molar ratio of Sr is within the range of 0.45 or more and 1.1 or less, the molar ratio of Ca is within the range of more than 0 and less than 0.55, the molar ratio of Eu is within the range of more than 0 and 0.033 or less, the molar ratio of the sum of Sr, Ca, and Eu is 1.1 or less, the molar ratio of Si is within the range of more than 0.81 and 1.21, and the molar ratio of N is within the range of more than 2.25 and 3.85 or less; and on the surface of the phosphor core particle, a first film containing at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al and oxygen, and a second film containing at least Si, in this order from the phosphor core particle side.

[0041] The nitride phosphor is preferably manufactured by the manufacturing method according to an embodiment of the present invention.

[0042] Phosphor core particles The nitride phosphor preferably has a composition in which the phosphor core particles are represented by the following formula (I). Sr u Ca v Eu w Si x Al y N z (I) (In the above formula (I), u, v, w, x, y, and z are numbers satisfying 0.5 ≦ u ≦ 1.0, 0 < v < 0.5, 0 < w ≦ 0.03, u + v + w ≦ 1.0, 0.9 ≦ x ≦ 1.1, 0.9 ≦ y ≦ 1.1, and 2.5 ≦ z ≦ 3.5, respectively.)

[0043] In formula (I), the variable w representing the molar ratio of Eu, which is the activating element of the phosphor core particles, may be in the range of 0.0001 or more and 0.03 or less (0.0001 ≦ w ≦ 0.03), and more preferably in the range of 0.001 or more and 0.025 or less (0.001 ≦ w ≦ 0.025). In formula (I), the variable v representing the molar ratio of Ca may be in the range of 0.001 or more and less than 0.5 (0.001 ≦ v < 0.5), and may be in the range of 0.005 or more and less than 0.5 (0.005 ≦ v < 0.5).

[0044] The volume average particle diameter of the phosphor core particle is preferably in the range of 1 μm to 40 μm, more preferably in the range of 5 μm to 35 μm, even more preferably in the range of 5 μm to 30 μm, and even more preferably in the range of 10 μm to 30 μm. When the volume average particle diameter of the phosphor core particle is in the range of 1 μm to 40 μm, even when a first film and a second film are formed, the luminous efficiency of the nitride phosphor can be maintained while suppressing chromaticity change. The volume average particle diameter of the phosphor core particle refers to the volume average particle diameter (median diameter: Dm) at which the cumulative frequency from the small diameter side reaches 50% in the volume-based particle size distribution measured using a laser diffraction particle size distribution analyzer (e.g., product name MASTER SIZER 3000, manufactured by MALVERN).

[0045] First membrane The nitride phosphor includes a first film on the surface of the phosphor core particle, the first film containing oxygen and at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al. The first film can be formed by contacting the phosphor core particle with water and performing the pre-heat treatment or the first heat treatment. By including the first film on the surface of the nitride phosphor core particle, the elements that form the crystal structure of the phosphor core particle are less likely to react with carbon dioxide, moisture, etc., even in environments with relatively high temperatures and humidity. The first film protects the surface of the phosphor core particle from the external environment, further suppressing chromaticity change and improving durability.

[0046] The thickness of the first film is preferably in the range of 10 nm to 100 nm. The thicker the first film, the more difficult it is for carbon dioxide, moisture, etc., to react with elements contained near the surface of the phosphor core particle. However, if the first film is too thick, a nitride phosphor having the desired color tone may not be obtained. When the volume average diameter of the phosphor core particle is in the range of 1 μm to 40 μm, the thickness of the first film is preferably in the range of 10 nm to 100 nm. The thickness of the first film may be in the range of 20 nm to 100 nm, or in the range of 30 nm to 100 nm. The thickness of the first film may also be in the range of 10 nm to 50 nm, or in the range of 10 nm to 40 nm, or in the range of 10 nm to 30 nm. The thickness of the first film and the second film on the surface of the phosphor core particle can be measured from an SEM photograph of a backscattered electron image of a cross section of the nitride phosphor using, for example, a field emission scanning electron microscope (FE-SEM), by, for example, the method described in the examples below.

[0047] Second membrane The nitride phosphor includes, on the surface of the phosphor core particle, the first film and a second film containing at least Si, in this order from the phosphor core particle side. The second film can be formed by contacting urea, silicate, water, and the phosphor core particle and performing the first heat treatment, and preferably the density of the first film and the second film is increased by the second heat treatment. By further including the second film on the surface of the nitride phosphor phosphor core particle, the phosphor core particle is more stably protected from external environments of relatively high temperature and humidity, chromaticity change is more suppressed, and durability is further improved.

[0048] The thickness of the second film is preferably in the range of 10 nm to 200 nm, more preferably in the range of 10 nm to 150 nm. The thickness of the second film may be in the range of 20 nm to 150 nm, or in the range of 30 nm to 150 nm. The thickness of the second film may also be in the range of 10 nm to 50 nm, or in the range of 10 nm to 40 nm, or in the range of 10 nm to 30 nm. A thicker second film is preferable because it can suppress the intrusion of carbon dioxide and moisture and protect the phosphor core particles. On the other hand, if the second film is too thick, the first and second films formed on the surface of the phosphor core particle may prevent the nitride phosphor from having the desired color tone. When the volume average diameter of the phosphor core particle is in the range of 1 μm to 40 μm, the thickness of the second film is preferably in the range of 10 nm to 200 nm.

[0049] The molar ratio of Si to oxygen contained in the second film is preferably higher than that of Si to oxygen contained in the first film. Since the second film is formed by contacting phosphor core particles with urea, silicate, and water and performing a first heat treatment, it is presumed that the second film contains silicon dioxide produced by the reaction of urea and silicate. If the molar ratio of Si to oxygen contained in the second film is higher than that of Si to oxygen contained in the first film, the second film becomes a stable protective film, and the phosphor core particles are more stably protected. The molar ratio of Si to oxygen contained in the first film or the second film refers to the sum of the molar ratio of Si and the molar ratio of oxygen contained in the first film or the second film.

[0050] The nitride phosphor preferably absorbs light in the wavelength range of 400 nm to 570 nm, which is the shorter wavelength region of ultraviolet to visible light, and emits fluorescence with an emission peak wavelength in the range of 600 nm to 670 nm. The nitride phosphor is more preferably excited by light in the wavelength range of 400 nm to 570 nm and has an emission peak wavelength in the range of 610 nm to 650 nm, and even more preferably has an emission peak wavelength in the range of 610 nm to 640 nm. The half-width of the emission spectrum of the nitride phosphor is, for example, 80 nm or less, preferably 75 nm or less. The half-width refers to the full width at half maximum (FWHM) of the emission peak in the emission spectrum, and refers to the wavelength width of the emission peak that represents 50% of the maximum value of the emission peak in the emission spectrum.

[0051] The nitride phosphor can be used in combination with an excitation light source such as an LED or LD for light emitting devices used in lighting devices, backlights for liquid crystal display devices, and the like.

[0052] The excitation light source used in the light emitting device can be an excitation light source that emits light in the wavelength range of 400 nm to 570 nm. By using an excitation light source in this wavelength range, a light emitting device with high luminescence intensity of the nitride phosphor can be provided. The light emitting element used as the excitation light source for the light emitting device preferably has an emission peak wavelength in the range of 420 nm to 500 nm, more preferably in the range of 420 nm to 460 nm.

[0053] As a light-emitting element, nitride semiconductors (In X Al Y Ga 1-X-Y It is preferable to use a semiconductor light-emitting element using a semiconductor light-emitting element having a wavelength of 0≦X, 0≦Y, X+Y≦1. By using a semiconductor light-emitting element as an excitation light source for a light-emitting device, it is possible to obtain a stable light-emitting device that is highly efficient, has high output linearity relative to input, and is resistant to mechanical shock. The half-width of the emission spectrum of the light-emitting element is preferably, for example, 30 nm or less.

[0054] The light emitting device may use, for example, a nitride phosphor including phosphor core particles having a composition represented by formula (I), a first film including at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al and oxygen, and a second film including at least Si. The light emitting device may also use phosphors other than nitride phosphors. For example, a nitride phosphor may be used as the first phosphor, and a second phosphor having an emission peak wavelength different from that of the first phosphor may be used. As the first phosphor, one phosphor may be used alone, or two or more phosphors may be used in combination, as long as the first phosphor has an emission peak wavelength within the desired wavelength range. As the second phosphor, one phosphor may be used alone, or two or more phosphors may be used in combination, as long as the second phosphor has an emission peak wavelength within the desired wavelength range.

[0055] An example of a light emitting device will be described with reference to the drawings. Figure 7 is a schematic cross-sectional view showing an example of a light emitting device. This light emitting device is an example of a surface-mounted light emitting device.

[0056] The light emitting device 100 includes a package having a recess formed by lead electrodes 20, 30 and a molded body 40, a light emitting element 10, and a sealing member 50 that covers the light emitting element 10. The light emitting element 10 is disposed in the recess of the package and is electrically connected to a pair of positive and negative lead electrodes 20, 30 provided on the molded body 40 by conductive wires 60. The sealing member 50 fills the recess, covers the light emitting element 10, and seals the recess of the package. The sealing member 50 includes, for example, a phosphor 70 that converts the wavelength of light from the light emitting element 10 and a resin. The phosphor 70 further includes a first phosphor 71 and a second phosphor 72. The pair of positive and negative lead electrodes 20, 30 are partially exposed on the outer surface of the package. The light emitting device 100 emits light when power is supplied from an external source via the lead electrodes 20, 30.

[0057] The sealing member 50 contains a resin and a phosphor 70, and is formed so as to cover the light emitting element 10 placed in the recess of the light emitting device 100. [Example]

[0058] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0059] Preparation of phosphor core particles The composition contains Sr, Ca, Eu, Al, Si, and N. When the molar ratio of Al in the composition is 1, the molar ratios of Sr, Ca, Eu, and Si were measured so that the molar ratios of Sr, Ca, Eu, and Si were as follows: u The raw materials were weighed in a glove box with an inert atmosphere so that the molar ratio of the raw materials charged was Sr:Ca:Eu:Al:Si=0.937:0.049:0.014:1.0:1.0, and the raw materials were mixed to obtain a raw material mixture. The raw material mixture was filled into a crucible made of boron nitride and heat-treated in a nitrogen gas atmosphere at a gas pressure of 0.92 MPa (1.02 MPa absolute pressure) at a temperature of 1900°C to 2100°C for 0.5 hours to 24 hours. The raw material was mixed in a glove box with an inert atmosphere so that the molar ratio of the raw materials charged was Sr:Ca:Eu:Al:Si=0.937:0.049:0.014:1.0:1.0. The raw material mixture was then heat-treated in a nitrogen gas atmosphere at a gas pressure of 0.92 MPa (1.02 MPa absolute pressure) at a temperature of 1900°C to 2100°C for 0.5 hours to 24 hours. 0.937 Ca 0.049 EU 0.014 A fired material was obtained that would become a phosphor core having a composition represented by Al1SiN3. This fired material was then dispersed and classified to obtain phosphor core particles.

[0060] Example 1 Pre-heat treatment 400% by volume of deionized water was added to 100% by volume of the obtained phosphor core particles, and the phosphor core particles were brought into contact with the water and heat-treated in an air atmosphere at atmospheric pressure (0.10 MPa) and a temperature of 120°C for 9 hours. After the pre-heat treatment, the phosphor core particles were washed with deionized water and filtered to obtain pre-heat-treated phosphor core particles. The pre-heat-treated phosphor core particles were dried in a dryer at a temperature of 100°C for 10 hours. After drying, a first film containing the elements Sr, Al, Si, and N, as well as oxygen, was formed on the surface of the phosphor core particles.

[0061] First heat treatment 400% by volume of deionized water was added to 100% by volume of phosphor core particles bearing the first film on their surfaces, obtained by the pre-heat treatment. 16% by mass of potassium silicate (K2SiO3) and 6% by mass of urea were added to 100% of the phosphor core particles bearing the first film. The phosphor core particles, water, potassium silicate, and urea were contacted and subjected to a first heat treatment in an air atmosphere at atmospheric pressure (0.10 MPa) at a temperature of 90 to 100°C for 6 hours. In the first heat treatment, potassium silicate and urea were used in an amount such that the molar ratio was 1:1. After the first heat treatment, the phosphor core particles were washed with deionized water and filtered to obtain first heat-treated phosphor core particles. The first heat-treated phosphor core particles were then dried in a dryer at 100°C for 10 hours. After drying, a first film containing Sr, Al, Si, and N elements and oxygen, and a second film containing at least Si were formed on the surface of the phosphor core particles from the phosphor core particle side. The second film also contained silicon dioxide (SiO2) produced by the hydrolysis reaction of urea and potassium silicate.

[0062] Second heat treatment The phosphor core particles containing the first film and the second film obtained by the first heat treatment were packed into an alumina crucible and subjected to a second heat treatment in an air atmosphere at atmospheric pressure (0.10 MPa) at a temperature of 400°C for 10 hours. After the second heat treatment, the particles were allowed to cool to room temperature, yielding a nitride phosphor of Example 1 having the first film and the second film on the surface of the phosphor core particle in that order from the phosphor core particle side. The heat treatment conditions for Example 1 and each of the examples and comparative examples described below are shown in Table 1 below.

[0063] Example 2 A nitride phosphor of Example 2 was obtained in the same manner as in Example 1, except that the second heat treatment was carried out at a temperature of 400° C. for 3 hours.

[0064] Example 3 A nitride phosphor of Example 3 was obtained in the same manner as in Example 1, except that the second heat treatment was carried out at a temperature of 350° C. for 3 hours.

[0065] Example 4 The nitride phosphor of Example 4 was obtained in the same manner as in Example 1, except that the pre-heat treatment was not carried out.

[0066] Comparative Example 1 Phosphor core particles that had not been subjected to the pre-heat treatment, first heat treatment, or second heat treatment were washed by adding 400% or more by volume of deionized water to 100% by volume of the phosphor core particles, and the washed phosphor core particles were brought into contact with an acidic solution (hydrochloric acid solution) with a pH of about 1 to 2 while stirring for 10 minutes to 5 hours, and after removing the supernatant, washed with deionized water. The phosphor core particles after the washing treatment were used as the nitride phosphor of Comparative Example 1.

[0067] Comparative Example 2 A nitride phosphor of Comparative Example 2 was obtained in the same manner as in Example 1, except that a pre-heat treatment was carried out once at a temperature of 120° C. for 9 hours and the first heat treatment was not carried out.

[0068] Comparative Example 3 A pre-heat treatment was performed once in the same manner as in Comparative Example 2, and after drying in the same manner as in Example 1, a second pre-heat treatment was performed at a temperature of 120°C for 9 hours, and the nitride phosphor of Comparative Example 3 was obtained in the same manner as in Example 1, except that the first heat treatment was not performed.

[0069] Comparative Example 4 The nitride phosphor of Comparative Example 4 was obtained in the same manner as in Example 1, except that pre-heat treatment was performed twice in the same manner as in Comparative Example 3, and then drying was performed in the same manner as in Example 1, followed by a third pre-heat treatment at a temperature of 120°C for 9 hours, and the first heat treatment was not performed.

[0070] Evaluation of nitride phosphors Volume average particle size (Dm) For each nitride phosphor in the Examples and Comparative Examples, the volume-average particle size (median diameter: Dm) at which the cumulative frequency from the small diameter side in the volume-based particle size distribution measured using a laser diffraction particle size distribution analyzer (product name: MASTER SIZER3000, manufactured by MALVERN) reached 50% was measured. The results are shown in Table 1 below.

[0071] Light-emitting properties The luminescence characteristics of each nitride phosphor were measured. The luminescence characteristics of the nitride phosphors were measured using a spectrofluorometer (product name: QE-2000, manufactured by Otsuka Electronics Co., Ltd.) with an excitation light wavelength of 450 nm. The relative luminescence intensity (%) and peak wavelength (λp: nm) of each nitride phosphor were determined from the measured luminescence spectrum. The relative luminescence intensity (%) is calculated relative to the relative luminescence intensity of the nitride phosphor of Comparative Example 1, with the relative luminescence intensity being 100%. The results are shown in Table 1. Figure 3 shows the luminescence spectra of the nitride phosphors of Example 1 and Comparative Example 1.

[0072] Durability evaluation (high temperature and humidity evaluation) The chromaticity (x, y) of each nitride phosphor on the CIE (Commission Internationale d'Eclarirage) chromaticity coordinates was measured using a spectrofluorometer (product name: QE-2000, manufactured by Otsuka Electronics Co., Ltd.) with an excitation light wavelength of 450 nm. A durability test was performed by storing each nitride phosphor for 72 hours in an environmental test chamber at a temperature of 130°C and a relative humidity of 100%. The y value on the chromaticity coordinates of the nitride phosphor before the durability test was taken as the initial value, and the absolute value of the difference in the y value of the nitride phosphor after the durability test was measured as Δy. The results are shown in Table 1 below.

[0073] [Table 1]

[0074] Film Thickness Measurement The first and second films were visually recognized from SEM photographs of the cross sections of each nitride phosphor of Examples 1 and 4 and Comparative Examples 1 to 4, and the thickness of the first film or the second film was measured for each location in each nitride phosphor. Specifically, SEM photographs of the cross sections of the nitride phosphors of each Example and Comparative Example were obtained using the method for obtaining backscattered electron images of SEM photographs described below, and SEM photographs of the cross sections of one to three nitride phosphors of each Example and Comparative Example were visually observed, and the thickness of the first film or the second film was measured at one to three locations in the cross section of each phosphor. In the SEM photographs of the cross sections of the nitride phosphors obtained by the method described below, the thickness of the first film or the second film that can be visually recognized for each nitride phosphor varies for each individual nitride phosphor particle and varies for each location in the cross section of the nitride phosphor. Table 2 below shows the ranges obtained by measuring the thickness of the first film or the second film of the nitride phosphors of each Example and Comparative Example.

[0075] [Table 2]

[0076] As shown in Table 1, the nitride phosphors of Examples 1 to 4 exhibited smaller chromaticity change Δy values than the comparative examples, even when placed in high-temperature and high-humidity environments. From these results, it was inferred that both the first and second films functioned as protective films, suppressing chromaticity change and improving durability. The nitride phosphors of Examples 1 to 4 had higher relative luminous intensities than the nitride phosphor of Comparative Example 1, but the nitride phosphors of Comparative Examples 2 to 4 also exhibited higher relative luminous intensities than Comparative Example 1, and there was no significant change in the emission peak wavelength. From these results, it was confirmed that the nitride phosphors of Examples 1 to 4 maintained high luminous efficiency even when the first and second films were formed by the first and second heat treatments. Example 3 exhibited a chromaticity change Δy value nearly equivalent to that of Example 1 or 2. It was inferred that the density of the first and second films was improved and their function as protective films was improved when the second heat treatment temperature was 350°C or higher, thereby improving durability. The nitride phosphor of Example 4 was not subjected to a pre-heat treatment, and therefore the thickness of the first film tended to be relatively thin, as shown in Table 2. Therefore, the nitride phosphor of Example 4 had a larger chromaticity change Δy value than Examples 1 to 3, but it was still about one-tenth of the chromaticity change Δy of Comparative Example 1.

[0077] As shown in Figure 3, the emission spectrum of Example 1 and the emission spectrum of Comparative Example 1 almost overlap, and it was confirmed that the nitride phosphor containing a double film of a first film and a second film on the surface of the phosphor core particle maintains high emission intensity without changing the emission spectrum, similar to the nitride phosphor without a film.

[0078] The nitride phosphor of Comparative Example 1 did not have a first film or a second film, and therefore, when placed in a high-temperature, high-humidity environment, the chromaticity change Δy value was larger than that of the Examples, suggesting that the nitride phosphor had deteriorated. The nitride phosphors of Comparative Examples 2 to 4 were subjected to a pre-heat treatment and a second heat treatment, but because they did not undergo a first heat treatment, no second film was formed, and the chromaticity change Δy value was larger than that of the nitride phosphors of Examples 1 to 4, indicating that durability was not improved. As shown in Table 2, the thickness of the first film of the nitride phosphors of Comparative Examples 2 to 4 increased with increasing number of pre-heat treatments. However, the nitride phosphors of Comparative Examples 2 to 4 sometimes contained cracks in the first film as the film thickness increased, and the chromaticity change Δy value was larger than that of the Examples, indicating that durability was not improved.

[0079] SEM photo-Secondary electron image Using a scanning electron microscope (SEM, product name: SU3500, manufactured by Hitachi High-Technologies Corporation), SEM photographs were taken of the nitride phosphors of Comparative Examples 1 to 3 and Example 1. Fig. 5 is an SEM photograph of the nitride phosphor of Example 1, and Fig. 6 is an SEM photograph of the nitride phosphor of Comparative Example 1.

[0080] SEM photo-backscattered electron image The obtained nitride phosphor was embedded in epoxy resin, and after the resin was cured, it was cut so that the cross section of the nitride phosphor was exposed. The surface was polished with sandpaper and then finished with a cross-section polisher (CP). A field emission scanning electron microscope (FE-SEM, product name: SU8230, manufactured by Hitachi High-Technologies Corporation) was used to obtain SEM photographs of backscattered electron images of the cross sections of the nitride phosphors of Examples 1 and 4 and Comparative Examples 1 to 4. Figure 4 is an SEM photograph of a backscattered electron image of the cross section of a particle of the nitride phosphor of Example 1.

[0081] Composition analysis The nitride phosphor of Example 1 was embedded in epoxy resin, the resin was cured, and then the nitride phosphor was cut to expose its cross section. The surface was polished with sandpaper and then finished with a cross-section polisher (CP). Images were then taken with a field-emission scanning electron microscope (FE-SEM, product name: SU8230, manufactured by Hitachi High-Technologies Corporation). The phosphor core particle (P6 in FIG. 4), the first film (P5 in FIG. 4), and the second film (P4 in FIG. 4) in the cross section of Example 1 were subjected to composition analysis using an energy-dispersive X-ray fluorescence spectrometer (EDX, SDD detector, manufactured by HORIBA, Ltd., accelerating voltage: 5 kV). The results are shown in Table 3. In Table 3, the molar ratios of the elements contained in the phosphor core particle (P6 in FIG. 4), the first film (P5 in FIG. 4), and the second film (P4 in FIG. 4) were calculated with the molar ratio of Al set to 1.

[0082] [Table 3]

[0083] As shown in Table 3, the molar ratio of Al to Si in the phosphor core particle (P6 in FIG. 4) of the nitride phosphor of Example 1 was 1:0.99, and the Sr 0.937 Ca 0.049 EU 0.014 The molar ratio of Al to Si in the composition represented by AlSiN3 was maintained at 1:1. The first film (P5 in FIG. 4) portion of the nitride phosphor of Example 1 had a higher molar ratio of oxygen (O) than the phosphor core particle portion, and it was confirmed that a first film containing Sr, Al, Si, N, and O was formed. The second film (P4 in FIG. 4) portion of the nitride phosphor of Example 1 had a higher molar ratio of Si to O than the phosphor core particle and first film portion when the molar ratio of Al was set to 1, and it was confirmed that a second film containing at least Si generated in the first heat treatment was formed.

[0084] As shown in Figure 4, in the SEM photograph of the cross section of the nitride phosphor of Example 1, it was confirmed that a first film 2 (P5) and a second film 3 (P4) were formed on the surface of the phosphor core particle 1 (P6) in this order from the phosphor core particle 1 side.

[0085] As shown in Fig. 5, the SEM photograph showed that the surface of the nitride phosphor of Example 1 was rough, and deposits on the surface of the nitride core particles were observed. On the other hand, as shown in Fig. 6, the SEM photograph showed that the surface of the nitride phosphor of Comparative Example 1 was smoother and had less deposits than the surface of the nitride phosphor of Example 1. [Industrial Applicability]

[0086] The nitride phosphor of one embodiment of the present invention can be suitably used in light-emitting devices that are applied to lighting sources, LED displays, backlight sources for liquid crystal displays, traffic lights, illuminated switches, light sources for projectors, various sensors, various indicators, and the like. [Explanation of symbols]

[0087] 1: phosphor core particle, 2: first film, 3: second film, 10: light emitting element, 40: molded body, 50: sealing member, 70: phosphor, 100: light emitting device.

Claims

1. a phosphor core particle having a composition containing Sr, Ca, Eu, Si, Al, and N, wherein, when the molar ratio of Al in the composition is taken as 1, the molar ratio of Sr is within the range of 0.45 or more and 1.1 or less, the molar ratio of Ca is within the range of more than 0 and less than 0.55, the molar ratio of Eu is within the range of more than 0 and 0.033 or less, the molar ratio of the sum of Sr, Ca, and Eu is 1.1 or less, the molar ratio of Si is within the range of more than 0.81 and 1.21, and the molar ratio of N is within the range of more than 2.25 and 3.85 or less; and a first film containing, on a surface of the phosphor core particle, in this order from the phosphor core particle side, at least one element selected from the group consisting of Sr, Ca, Eu, Si, and Al, and oxygen, and a second film containing at least Si and oxygen; The nitride phosphor, wherein the first film contains nitrogen and the second film does not contain nitrogen.

2. 2. The nitride phosphor according to claim 1, wherein the phosphor core particle has a composition represented by the following formula (I): Sr ｕ Ca ｖ Eu ｗ Yes ｘ Al ｙ N ｚ (I) (In the formula (I), u, v, w, x, y, and z are numbers that satisfy the following conditions: 0.5≦u≦1.0, 0<v<0.5, 0<w≦0.03, u+v+w≦1.0, 0.9≦x≦1.1, 0.9≦y≦1.1, and 2.5≦z≦3.5.)

3. 3. The nitride phosphor according to claim 1, wherein the molar ratio of nitrogen in the first film is greater than 0.00 mol %, and the molar ratio of nitrogen in the second film is 0.00 mol %.

4. 4. The nitride phosphor according to claim 1, wherein the volume average particle size of the phosphor core particles is in the range of 1 μm or more and 40 μm or less.

5. 5. The nitride phosphor according to claim 1, wherein the first film has a thickness in the range of 10 nm to 100 nm.

6. 6. The nitride phosphor according to claim 1, wherein the second film has a thickness of 10 nm or more and 200 nm or less.

7. The nitride phosphor according to claim 1 , wherein the second film comprises silicon dioxide.

8. 8. A nitride phosphor according to claim 1, wherein the molar ratio of elements contained in the first film is calculated by setting the molar ratio of Al contained in the first film to 1, and the molar ratio of oxygen contained in the first film is greater than the molar ratio of oxygen contained in the phosphor core particles when the molar ratio of Al in the phosphor composition is set to 1.

9. 9. The nitride phosphor according to claim 8, wherein the second film contains Al, the molar ratio of the elements contained in the second film is calculated by taking the molar ratio of Al contained in the second film to be 1, and the molar ratio of oxygen contained in the second film is greater than the molar ratio of oxygen contained in the first film.

10. A light emitting device comprising the nitride phosphor according to claim 1 and an excitation light source.

Images