Nitride phosphors and methods for producing the same

Abstract

To provide a production method of a nitride phosphor capable of showing high light emission intensity.SOLUTION: A production method of a nitride phosphor includes: obtaining a first heat-treated object having a crystallite diameter of 150 nm or more by heat-treating a compound containing at least one kind of rare earth element selected from the group consisting of Y, La, Ce, Lu and Gd at a temperature in a range of 800°C or more and 1,800°C or less; and obtaining a second heat-treated object by heat-treating at a temperature in a range of 1,200°C or more and 1,800°C or less, a mixture containing the first heat-treated object, and if necessary as the raw materials, an M source containing at least one kind of rare earth element M selected from the group consisting of Y, Lu and Gd, and an La source, an Si source and a Ce source, and adjusted so that a preparation composition of the raw materials is represented by composition formula LawMxSi6 Ny:Cez. In the composition formula, w, x, y and z satisfy 0.5≤w≤4.5, 0<x≤1.5, 0≤y≤12, 0<z≤1.5, 0.15<(x+z)<3.0, 3.0≤(w+x+z)≤7.5.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to nitride phosphors and methods for producing the same. [Background technology]

[0002] Light-emitting devices are known that combine light-emitting elements such as LEDs (Light Emitting Diodes) and LDs (Laser Diodes) with phosphors, converting a portion of the light from the light-emitting element into a different color using the phosphor, and emitting a mixed color of light from the light-emitting element and the light from the phosphor. As a phosphor used in such a light-emitting device, for example, (La,Y)3Si6N is described in Patent Documents 1 and 2. 11 :Ce (hereinafter sometimes abbreviated as "LYSN"), or La3Si6N 11 A nitride phosphor having a composition represented by :Ce (hereinafter sometimes abbreviated as "LSN") and a method for producing the same have been proposed. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2017 / 170609 [Patent Document 2] Japanese Patent Publication No. 2020-96175 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] For such LYSN phosphors, even higher luminescence intensity is required. One aspect of this disclosure aims to provide a method for producing a nitride phosphor that can exhibit high luminescence intensity. [Means for solving the problem]

[0005] The first aspect includes heat-treating a compound containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), lutetium (Lu), and gadolinium (Gd) at a temperature within the range of 800 °C or higher and 1800 °C or lower to obtain a first heat-treated product having a crystallite size of 150 nm or more, and heat-treating a mixture prepared so that the raw materials, which include the first heat-treated product and, if necessary, a source of at least one rare earth element M selected from the group consisting of yttrium (Y), lutetium (Lu), and gadolinium (Gd), a lanthanum (La) source, a silicon (Si) source, and a cerium (Ce) source, have a charging composition represented by the following formula (1) at a temperature within the range of 1200 °C or higher and 1800 °C or lower to obtain a second heat-treated product. This is a method for manufacturing a nitride phosphor.

[0006] La w M x Si6N y :Ce z (1)

[0007] In formula (1), w, x, y, and z satisfy 0 ≦ w ≦ 4.5, 0 < x ≦ 1.5, 0 ≦ y ≦ 12, 0 < z ≦ 1.5, 0.15 < (x + z) < 3.0, and 3.0 ≦ (w + x + z) ≦ 7.5.

[0008] The second aspect is a nitride phosphor having a crystallite size of 48 nm or less and having a composition represented by the following formula (2). La p M q Si6N r :Ce s (2)

[0009] In formula (2), p, q, r, and s satisfy 0.5 ≦ p ≦ 3.05, 0 < q ≦ 1.2, 10 ≦ r ≦ 12, 0 < s ≦ 1.2, 0.05 < (q + s) ≦ 2.4, and 2.9 ≦ p + q + s ≦ 3.1.

Advantages of the Invention

[0010] According to the present disclosure, it is possible to provide a method for manufacturing a nitride phosphor that can exhibit high emission intensity.

Brief Description of Drawings

[0011] [Figure 1] This is an example of a scanning electron microscope (SEM) image of yttrium oxide used in Comparative Example 1. [Figure 2] This is an example of an SEM image of yttrium oxide used in Example 1. [Figure 3] This is an example of the emission spectrum of the nitride phosphor according to Example 1 and Comparative Example 1. [Figure 4] This is an example of the emission spectrum of the nitride phosphor according to Example 2 and Comparative Example 3. [Figure 5] This is an example of the emission spectrum of the nitride phosphor according to Examples 3 to 5 and Comparative Example 4.

Modes for Carrying Out the Invention

[0012] In this specification, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Also, the content of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. Furthermore, the upper and lower limits of the numerical ranges described in this specification can be arbitrarily selected and combined. In this specification, the half-value width of the phosphor means the wavelength width (full width at half maximum; FWHM) of the emission spectrum at which the emission intensity becomes 50% with respect to the maximum emission intensity in the emission spectrum of the phosphor. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples of a method for manufacturing a nitride phosphor for embodying the technical idea of the present invention, and the present invention is not limited to the method for manufacturing a nitride phosphor shown below.

[0013] Method for Manufacturing Nitride Phosphor The method for manufacturing a nitride phosphor includes a first heat treatment step of heat-treating a compound containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), lutetium (Lu), and gadolinium (Gd) (hereinafter also simply referred to as "rare earth compound") at a first heat treatment temperature within the range of 800°C or higher and 1800°C or lower to obtain a first heat-treated product having a crystallite size of 150 nm or more, and a second heat treatment step of heat-treating a mixture containing the first heat-treated product and at least one selected from the group consisting of a source M of at least one rare earth element M selected from the group consisting of yttrium (Y), lutetium (Lu), and gadolinium (Gd), a source of lanthanum (La), a source of silicon (Si), and a source of cerium (Ce) at a second heat treatment temperature within the range of 1200°C or higher and 1800°C or lower to obtain a second heat-treated product. The mixture is prepared so that the content ratios of La, rare earth element M, Si, and Ce have a charging composition represented by the following formula (1).

[0014] La w M x Si6N y :Ce z (1)

[0015] In formula (1), w, x, y, and z may satisfy 0 ≤ w ≤ 4.5, 0 < x ≤ 1.5, 0 ≤ y ≤ 12, 0 < z ≤ 1.5, 0.15 < (x + z) < 3.0, and 3.0 ≤ (w + x + z) ≤ 7.5, and preferably satisfy 2.0 ≤ w ≤ 4.0, 0.3 < x ≤ 1.2, 0 ≤ y ≤ 11.5, 0 < z ≤ 1.2, 0.3 < (x + z) < 2.4, and 3.2 ≤ (w + x + z) ≤ 5.8.

[0016] By using a rare earth compound that has been preheated at a predetermined first heat treatment temperature as part of the raw materials to produce a nitride phosphor having a predetermined composition, the luminescence intensity of the produced nitride phosphor is improved. This can be considered as follows, for example: By preheating the rare earth compound at a predetermined temperature, for example, the crystallinity of the rare earth compound that serves as the raw material for the nitride phosphor is improved, making it possible to control the reactivity of the raw material. As a result, for example, if the rare earth compound is a yttrium compound, the reaction system will consist of a reaction between a La source (e.g., LaN) and a Si source (e.g., Si3N4) to form a core LSN (e.g., La3Si6N4). 11 It is believed that the formation of a crystalline structure of ) is followed by a substitution reaction with a yttrium compound (e.g., Y2O3) which proceeds stepwise in the second heat treatment temperature range, without disrupting the crystalline structure of the nucleus, thereby generating the desired nitride phosphor and achieving improved luminescence intensity. Furthermore, it is thought that the yttrium compound (e.g., Y2O3) and the nucleus LSN become more readily soluble (react) together, leading to improved luminescence intensity.

[0017] In the first heat treatment step, a rare earth compound containing at least one rare earth element selected from the group consisting of Y, La, Ce, Lu, and Gd is heat-treated. The rare earth compound preferably contains at least one selected from the group consisting of Y, La, and Ce, and more preferably contains at least Y. The rare earth compound may be at least one selected from the group consisting of oxides, halides (e.g., fluorides, chlorides, etc.), nitrides, alloys, etc., containing rare earth elements, and preferably at least one selected from the group consisting of oxides, fluorides, and nitrides. The rare earth compound subjected to heat treatment in the first heat treatment step may be a single compound or a combination of two or more compounds. The purity of the rare earth compound may be, for example, 95% or higher, preferably 97% or higher, or 98% or higher. The upper limit of the purity of the rare earth compound may be, for example, 99.999% or lower.

[0018] The first heat treatment temperature in the first heat treatment step may be, for example, 800°C or more and 1800°C or less, preferably 900°C or more, 1000°C or more, 1200°C or more, 1300°C or more, or 1350°C or more, and also preferably 1700°C or less, 1650°C or less, 1550°C or less, 1500°C or less, or 1450°C or less.

[0019] The heat treatment in the first heat treatment step may include raising the temperature to a predetermined first heat treatment temperature, maintaining the first heat treatment temperature, and lowering the temperature from the first heat treatment temperature. The rate of raising the temperature to the first heat treatment temperature may be, for example, 0.1°C / min or more and 20°C / min or less, preferably 0.5°C / min or more, or 1°C / min or more, and preferably 15°C / min or less, or 10°C / min or less, as a rate of raising the temperature from room temperature. The heat treatment time for maintaining the first heat treatment temperature may be, for example, 0.5 hours or more and 100 hours or less, preferably 2 hours or more, or 10 hours or more, and preferably 20 hours or less, or 10 hours or less. The rate of lowering the temperature from the first heat treatment temperature may be, for example, 1°C / min or more and 600°C / min or less, as a rate of lowering the temperature to room temperature.

[0020] The atmosphere in the first heat treatment step may be, for example, an oxygen-containing atmosphere or an atmospheric atmosphere. Alternatively, the atmosphere in the first heat treatment step may be an inert atmosphere containing noble gases such as nitrogen or argon, or a reducing atmosphere containing reducing gases such as hydrogen. The atmosphere for the first heat treatment may be appropriately selected depending on the type of rare earth compound.

[0021] The first heat-treated product obtained in the first heat treatment step may contain a rare earth compound having a crystallite size of, for example, 150 nm or more. The crystallite size of the first heat-treated product may be, for example, 150 nm or more and 600 nm or less, preferably 200 nm or more, or 250 nm or more, and also preferably 550 nm or less, 500 nm or less, 450 nm or less, or 400 nm or less.

[0022] The crystallite size of rare earth compounds contained in the first heat-treated material can be measured, for example, as follows: The XRD pattern of the rare earth compound sample is measured using an X-ray diffractometer. The crystallite size of the sample can be determined by fitting the XRD pattern obtained by measurement with the XRD pattern of the crystal structure model of the rare earth compound, which can be obtained from the International Diffraction Data Center (ICDD), using the Rietveld method.

[0023] The first heat-treated material has a specific surface area measured by the BET method, for example, 0.5 m². 2 / g or more 2.1m 2 It may be less than or equal to / g. The specific surface area of ​​the first heat-treated material, as measured by the BET method, is preferably 0.7m². 2 It may be 1.5 m or more, and preferably 1.5 m 2 It may be less than or equal to / g. The specific surface area measured by the BET method is measured using a single-point method with nitrogen gas, based on the BET (Brunauer Emmett Teller) theory.

[0024] The first heat-treated material may have a 50% particle size Dm corresponding to 50% of the cumulative total from the smallest diameter side in the volume-based particle size distribution, for example, between 6.5 μm and 12.0 μm. The 50% particle size Dm of the first heat-treated material may preferably be 7.5 μm or more, or 7.8 μm or more, and also preferably 11.5 μm or less, or 11.0 μm or less. The volume-based particle size distribution is measured using a laser diffraction particle size distribution analyzer.

[0025] In the second heat treatment step, a mixture containing the raw materials for the nitride phosphor is heat-treated at a second heat treatment temperature to obtain a second heat-treated product containing the nitride phosphor. The mixture subjected to the second heat treatment step contains at least the first heat-treated product. The mixture may contain an M source containing at least one rare earth element M selected from the group consisting of Y, Lu, and Gd, as well as an La source, a Si source, and a Ce source, and each element source may be prepared to have the charging composition shown in formula (1) above. The first heat-treated product may be included in the mixture as at least a part of at least one selected from the group consisting of the M source, La source, and Ce source, and may be included as at least a part of the M source. The at least one element source selected from the group consisting of the M source, La source, and Ce source in the mixture may each consist only of the first heat-treated product, or may contain the first heat-treated product as part of the element source. If the element source includes a first heat-treated product as part of it, the ratio of the number of moles of the first heat-treated product to the total number of moles of the element source may be, for example, 0.1 or more and 5.0 or less, preferably 0.3 or more and 4.5 or less. Here, the number of moles of the element source, etc. is based on the number of moles of the element contained in the element source, etc.

[0026] The M source may contain at least one element selected from the group consisting of Y, Lu, and Gd, and preferably at least Y. The molar content of Y relative to the total molar amount of rare earth element M contained in the M source may be, for example, 90% or more, preferably 95% or more, or 98% or more. The M source may be a compound containing a rare earth element M, a pure rare earth element M, an alloy containing a rare earth element M, etc., and may be at least one element selected from the group consisting of these. The compound containing a rare earth element M may be at least one element selected from the group consisting of oxides, halides (e.g., fluorides, chlorides, etc.), nitrides, alloys, etc., and preferably at least one element selected from the group consisting of oxides, fluorides, and nitrides. The compound containing a rare earth element M contained in the M source may be a single compound or a combination of two or more compounds.

[0027] The mixture may contain a first heat-treated product and a compound containing a rare earth element M as the M source. That is, the first heat-treated product may be a compound containing a rare earth element M. The first heat-treated product may be at least one selected from the group consisting of oxides, fluorides, and nitrides containing a rare earth element M, and may contain at least an oxide containing a rare earth element M. Furthermore, the rare earth compound contained in the first heat-treated product and the rare earth compound containing a rare earth element M other than the first heat-treated product may be the same or different.

[0028] The ratio of the number of moles of element M contained in the M source contained in the mixture may be, for example, greater than 0 and 1.5 or less, preferably 0.2 or more, or 0.3 or more, and preferably 1.4 or less, or 1.2 or less, when the amount of silicon (Si) contained in the mixture is 6 moles.

[0029] The La source may be a compound containing La, elemental La, an alloy containing La, etc., and may be at least one selected from the group consisting of these. The compound containing La may be at least one selected from the group consisting of oxides, halides (e.g., fluorides, chlorides, etc.), nitrides, alloys, etc., preferably at least one selected from the group consisting of oxides, fluorides and nitrides, and more preferably it may contain at least a nitride. The La source may be a single compound or a combination of two or more compounds.

[0030] The ratio of the number of moles of element La contained in the La source contained in the mixture may be, for example, 0 to 4.5 with respect to 6 moles of silicon (Si) contained in the mixture, preferably 1.2 or more, 1.5 or more, or 2.0 or more, and also preferably 4.3 or less, or 4.0 or less.

[0031] The Ce source may be a Ce-containing compound, elemental Ce, a Ce-containing alloy, etc., and may be at least one selected from the group consisting of these. The Ce-containing compound may be at least one selected from the group consisting of oxides, halides (e.g., fluorides, chlorides, etc.), nitrides, alloys, etc., preferably at least one selected from the group consisting of oxides, fluorides and nitrides, and more preferably it may contain at least fluorides. The Ce-containing compound contained in the Ce source may be a single compound or a combination of two or more compounds.

[0032] The ratio of the number of moles of element Ce contained in the Ce source contained in the mixture may be, for example, greater than 0 and 1.5 or less with respect to 6 moles of silicon (Si) contained in the mixture, preferably 0.05 or more, or 0.1 or more, and preferably 1.3 or less, or 1.2 or less.

[0033] The ratio of the total number of moles of rare earth element M and element Ce contained in the mixture may be, for example, greater than 0.15 and less than 3, preferably greater than 0.2 or greater than 0.3, and preferably less than 2.6 or less than 2.4, relative to 6 moles of silicon (Si) contained in the mixture. The ratio of the total number of moles of element La, rare earth element M, and element Ce source contained in the mixture may be, for example, 3 or more and 7.5 or less, preferably 3.1 or more, or 3.2 or more, and preferably 6.8 or less, 6.3 or less, or 5.8 or less, relative to 6 moles of silicon (Si) contained in the mixture.

[0034] The Si source may be a Si-containing compound, elemental Si, a Si-containing alloy, etc., and may be at least one selected from the group consisting of these. The Si-containing compound may be at least one selected from the group consisting of oxides, nitrides, etc., preferably at least one selected from the group consisting of oxides and nitrides, and more preferably it may contain at least a nitride. The Si-containing compound included in the Si source may be a single compound or a combination of two or more compounds.

[0035] The purity of the M source, La source, Si source, and Ce source may be, for example, 95% or higher, preferably 98% or higher, or 99% or higher. The upper limit of purity may be, for example, 99.99999% or lower.

[0036] The mixture may contain a halide such as a fluoride as at least part of at least one element source selected from the group consisting of an M source, a La source, and a Ce source. If the mixture contains a halide, the halide content relative to the total mass of the mixture may be, for example, 1% by mass or more and 40% by mass or less, preferably 2.5% by mass or more, or 5% by mass or more, and preferably 35% by mass or less, or 30% by mass or less.

[0037] The mixture is prepared by wet or dry mixing the first heat-treated material with at least one selected from the group consisting of M source, La source, Si source, and Ce source, using a mixer in a predetermined charging ratio. This promotes the solid-phase reaction and makes it possible to form particles of uniform size. In addition to ball mills commonly used in industry, grinders such as vibratory mills, roll mills, and jet mills may also be used as mixers. The specific surface area can also be increased by grinding with a grinder. Furthermore, in order to keep the specific surface area of ​​the powder within a certain range, classification can be performed using wet separators such as sedimentation tanks, hydrocyclones, and centrifuges commonly used in industry, or dry classifiers such as cyclones and air separators.

[0038] In the second heat treatment step, the prepared mixture is heat-treated at a predetermined second heat treatment temperature to obtain a second heat-treated product containing the desired nitride phosphor. The second heat treatment temperature in the second heat treatment step may be, for example, 1200°C or more and 1800°C or less, preferably 1300°C or more, or 1400°C or more, and also preferably 1700°C or less, 1600°C or less, or 1550°C or less.

[0039] The heat treatment in the second heat treatment step may include raising the temperature to a predetermined second heat treatment temperature, maintaining the second heat treatment temperature, and lowering the temperature from the second heat treatment temperature. The rate of raising the temperature to the second heat treatment temperature may be, for example, 0.1°C / min or more and 20°C / min or less, preferably 0.5°C / min or more, or 1°C / min or more, and preferably 15°C / min or less, 10°C / min or less, or 8°C / min or less, as a rate of raising the temperature from room temperature. The rate of raising the temperature to the second heat treatment temperature may include a plurality of heating rates. For example, it may include a first heating rate from room temperature to a third heat treatment temperature below the second heat treatment temperature, and a second heating rate from the third heat treatment temperature to the second heat treatment temperature. The third heat treatment temperature may be, for example, 1000°C or more and 1300°C or less, preferably 1100°C or more and 1300°C or less. The first heating rate may be, for example, 1°C / min or more and 20°C / min or less, preferably 2°C / min or more, or 3°C / min or more, and also preferably 10°C / min or less, or 8°C / min or less. The second heating rate may be, for example, 0.1°C / min or more and 10°C / min or less, preferably 0.5°C / min or more, or 0.8°C / min or more, and also preferably 5°C / min or less, or 3°C / min or less.

[0040] The heat treatment time for maintaining the second heat treatment temperature may be, for example, 1 hour or more and 30 hours or less, preferably 5 hours or more, or 10 hours or more, and preferably 20 hours or less, or 15 hours or less. The rate of cooling from the second heat treatment temperature may be, for example, 1°C / min or more and 600°C / min or less as the rate of cooling to room temperature.

[0041] The second heat treatment step may include heat-treating the mixture by maintaining several different temperatures for predetermined periods of time. That is, the second heat treatment step may include, for example, heat-treating the mixture while maintaining a fourth heat treatment temperature, and heat-treating the mixture that has been heat-treated at the fourth heat treatment temperature by maintaining a fifth heat treatment temperature higher than the fourth heat treatment temperature. The fourth heat treatment temperature may be, for example, 1200°C to 1400°C, preferably 1250°C to 1350°C. The fifth heat treatment temperature may be, for example, 1400°C to 1800°C, preferably 1450°C to 1750°C or 1500°C to 1700°C. The difference between the fifth heat treatment temperature and the fourth heat treatment temperature may be, for example, 100°C to 500°C, preferably 150°C or 200°C or more, and also preferably 450°C or 350°C or less.

[0042] The heat treatment at the fourth heat treatment temperature and the heat treatment at the fifth heat treatment temperature may be carried out consecutively, or the heat treatment at the fourth temperature may be cooled down and then the temperature may be raised to the fifth heat treatment temperature before proceeding. Furthermore, after the heat treatment at the fourth heat treatment temperature, the heat-treated material may be crushed and mixed before being heat-treated at the fifth heat treatment temperature.

[0043] The heating rate to the fourth heat treatment temperature may be, for example, 0.1°C / min or more and 20°C / min or less from room temperature, preferably 0.5°C / min or more, or 1°C / min or more, and preferably 15°C / min or less, 10°C / min or less, or 8°C / min or less. The heating rate to the fifth heat treatment temperature may be, for example, 0.1°C / min or more and 20°C / min or less from room temperature, preferably 0.5°C / min or more, or 1°C / min or more, and preferably 15°C / min or less, 10°C / min or less, or 8°C / min or less.

[0044] The heat treatment time for maintaining the fourth heat treatment temperature may be, for example, 1 hour or more and 30 hours or less, preferably 2 hours or more, or 4 hours or more, and also preferably 15 hours or less, or 8 hours or less. The heat treatment time for maintaining the fifth heat treatment temperature may be, for example, 1 hour or more and 30 hours or less, preferably 5 hours or more, or 8 hours or more, and also preferably 20 hours or less, or 15 hours or less.

[0045] The atmosphere in the second heat treatment step may be an inert atmosphere containing noble gases such as nitrogen and argon, or it may be a reducing atmosphere containing reducing gases such as hydrogen.

[0046] The second heat-treated product obtained in the second heat treatment step may be subjected to processes such as crushing, dispersion, washing, filtration, and classification. Washing can be performed, for example, by dispersing the second heat-treated product in water and separating the solid and liquid components. Solid-liquid separation can be performed by industrially commonly used methods such as filtration, suction filtration, pressure filtration, centrifugal separation, and decantation. The second heat-treated product may also be subjected to acid treatment. Acid treatment can be performed, for example, by dispersing the second heat-treated product in an acidic aqueous solution and separating the solid and liquid components. After acid treatment, washing with water and solid-liquid separation may be performed. After solid-liquid separation, drying treatment may be performed. Drying treatment can be performed using industrially commonly used equipment such as a vacuum dryer, a hot air heating dryer, a conical dryer, or a rotary evaporator.

[0047] Nitride phosphors The nitride phosphor has a crystallite size of 48 nm or less, and its composition may include lanthanum (La), cerium (Ce), at least one rare earth element M selected from the group consisting of yttrium (Y), lutetium (Lu), and gadolinium (Gd), silicon (Si), and nitrogen (N). The composition of the nitride phosphor may have a molar content ratio of lanthanum to 6 moles of silicon of 0.5 to 3.05, a molar content ratio of rare earth element M greater than 0 and 1.2 or less, a molar content ratio of cerium greater than 0 and 1.2 or less, and a molar content ratio of nitrogen of 10 to 12. In addition, the ratio of the total number of moles of rare earth element M and element Ce to 6 moles of silicon (Si) may be greater than 0.05 and 2.4 or less, and the ratio of the total number of moles of element La, rare earth element M, and element Ce source may be 2.9 to 3.1.

[0048] Nitride phosphors can be manufactured, for example, by the manufacturing method described above, and can achieve high emission intensity. The emission peak wavelength of the nitride phosphor may be, for example, 550 nm or more, preferably 555 nm or more, or 560 nm or more. The upper limit of the emission peak wavelength of the nitride phosphor may be, for example, 620 nm or less, preferably 615 nm or less, or 610 nm or less. The full width at half maximum in the emission spectrum of the nitride phosphor may be, for example, 100 nm or more, preferably 110 nm or more, 115 nm or more, or 120 nm or more. The upper limit of the full width at half maximum may be, for example, 150 nm or less, preferably 140 nm or less, or 130 nm or less.

[0049] The composition of the nitride phosphor may include lanthanum (La), cerium (Ce), at least one rare earth element M selected from the group consisting of yttrium (Y), lutetium (Lu), and gadolinium (Gd), silicon (Si), and nitrogen (N). Cerium may be included in the composition of the nitride phosphor as an activating element and may be the luminescent center of the nitride phosphor. The molar content of yttrium (Y) relative to the total molar amount of rare earth elements M contained in the nitride phosphor may be, for example, 90% or more, preferably 95% or more, or 98% or more.

[0050] The molar content of lanthanum in the nitride phosphor composition may be, for example, 0.5 to 3.05 relative to 6 moles of silicon, preferably 1.2 or more, or 2.0 or more, and preferably 2.7 or less, or 2.2 or less. The molar content of rare earth element M in the nitride phosphor composition may be, for example, greater than 0 and 1.2 or less relative to 6 moles of silicon, preferably 0.3 to 1.0. The molar content of cerium in the nitride phosphor composition may be, for example, greater than 0 and 1.2 or less relative to 6 moles of silicon, preferably 0.15 to 1.0. The molar content of nitrogen in the nitride phosphor composition may be, for example, 10 to 12 relative to 6 moles of silicon, preferably 10.5 to 11.5. The ratio of the total number of moles of rare earth element M and element Ce in the nitride phosphor composition may be greater than, for example, 0.05 and 2.4 or less relative to 6 moles of silicon, preferably 0.15 to 2.0, or 0.3 to 2.0. The ratio of the total number of moles of element La, rare earth element M, and element Ce source in the nitride phosphor composition may be greater than, for example, 2.9 to 3.1, preferably 2.95 to 3.05, relative to 6 moles of silicon Si. The nitride phosphor may have a composition represented by, for example, the following formula (2).

[0051] La p M q Si6N r :Ce s (2)

[0052] In formula (2), M may contain at least one selected from the group consisting of Y, Lu, and Gd, preferably containing at least Y. The molar content of Y in M may be 90% or more, preferably 95% or more. p, q, r, and s satisfy 0.5 ≤ p ≤ 3.05, 0 < q ≤ 1.2, 10 ≤ r ≤ 12, 0 < s ≤ 1.2, 0.05 < (q + s) ≤ 2.4, 2.9 ≤ p + q + s ≤ 3.1, and preferably satisfy 2.0 ≤ p ≤ 2.7, 0.3 ≤ q ≤ 1.0, 10.5 ≤ r ≤ 11.5, 0 < s ≤ 1.0, 0.3 ≤ (q + s) ≤ 2.0, 2.95 ≤ p + q + s ≤ 3.05.

[0053] In the composition of the nitride phosphor, a part of the rare earth element M may be substituted with at least one selected from the group consisting of Group 2 elements, preferably substituted with at least one selected from the group consisting of alkaline earth metal elements containing Mg. When a part of the rare earth element M is substituted with other elements other than rare earth elements, the molar content of the other elements in the rare earth element M is, for example, 10% or less, preferably 5% or less, or 3% or less. The lower limit of the molar content of the other elements may be, for example, 0.01% or more, preferably 1.0% or more. When a part of the rare earth element M is substituted with other elements, the total molar content of Y, Lu, and Gd with respect to the total molar amount of the rare earth element M contained in the nitride phosphor may be, for example, 90% or more, preferably 95% or more, or 98% or more. Also, the molar content of Y with respect to the total molar amount of the rare earth element M contained in the nitride phosphor may be, for example, 90% or more, preferably 95% or more, or 98% or more.

[0054] In the composition of nitride phosphors, some of the silicon may be substituted with at least one element selected from the group consisting of boron (B), aluminum (Al), gallium (Ga), and germanium (Ge). When some of the silicon is substituted with an element other than silicon, the molar content of the element other than silicon relative to the total number of moles of silicon and other elements in the composition is, for example, 50% or less, preferably 20% or less, or 10% or less. The lower limit of the molar content of the element other than silicon may be, for example, 0.01% or more, preferably 5% or more. When some of the silicon in the composition of nitride phosphors is substituted with an element other than silicon, the molar content of silicon relative to the total number of moles of silicon and other elements may be, for example, 90% or more, preferably 95% or more, or 98% or more.

[0055] The particle size distribution of the nitride phosphor may exhibit a single-peak particle size distribution from the viewpoint of luminescence intensity. The average particle size of the nitride phosphor may be, for example, 1 μm or more and 100 μm or less, preferably 5 μm or more and 70 μm or less, or 10 μm or more and 50 μm or less. Furthermore, the 50% particle size Dm, which corresponds to the cumulative 50% from the smallest diameter side in the volume-based particle size distribution, may be, for example, 1 μm or more and 100 μm or less, preferably 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more, and preferably 70 μm or less, 60 μm or less, or 50 μm or less.

[0056] The crystallite size of the nitride phosphor may be, for example, 50 nm or less, preferably 48 nm or less, 47 nm or less, 46 nm or less, 44 nm or less, or 42 nm or less. The lower limit of the crystallite size of the nitride phosphor may be, for example, 20 nm or more. When the crystallite size of the nitride phosphor is below a predetermined value, the luminescence intensity tends to improve and the full width at half maximum tends to become narrower. The crystallite size of the nitride phosphor is measured using XRD data of nitride phosphors registered in the ICDD database, in the same manner as the crystallite size of rare earth compounds. [Examples]

[0057] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0058] Reference example 1 Commercially available yttrium oxide (hereinafter also referred to as yttrium oxide 1) was placed in an alumina crucible and heated in air to 1000°C at a heating rate of 3°C / min to 7°C / min. After reaching 1000°C, it was held at that temperature for 4 hours for heat treatment. After the heat treatment, it was cooled to room temperature to obtain yttrium oxide 2 as the first heat-treated product. The crystallite size, 50% grain size Dm, and BET specific surface area of ​​yttrium oxide 1 before heat treatment and the obtained yttrium oxide 2 were measured using the method described later. The results are shown in Table 1. A scanning electron microscope (SEM) image of yttrium oxide 1 is shown in Figure 1.

[0059] Reference example 2 Yttrium 3 oxide was obtained in the same manner as in Reference Example 1, except that the heat treatment temperature was changed to 1300°C.

[0060] Reference example 3 Yttrium 4 oxide was obtained in the same manner as in Reference Example 1, except that the heat treatment temperature was changed to 1400°C.

[0061] Figure 2 shows an SEM image of yttrium-4 oxide. As shown in Figure 2, yttrium-4 oxide is formed as a collection of relatively larger particles, compared to yttrium-1 oxide shown in Figure 1. This is thought to be due to the larger crystallite size of yttrium-4 oxide compared to yttrium-1 oxide.

[0062] Reference example 4 Yttrium 5 oxide was obtained in the same manner as in Reference Example 1, except that the heat treatment temperature was changed to 1500°C.

[0063] Reference example 5 Yttrium 6 oxide was obtained in the same manner as in Reference Example 1, except that the heat treatment temperature was changed to 1600°C.

[0064] Measurement of crystallite size XRD measurements (X-ray Diffraction, CuKα, tube voltage: 40kV, tube current: 20mA, scanning range: within 10° to 70° (10°≦2θ≦70°), radiation source: CuKα, scanning axis: 2θ / θ, measurement method: FT, coefficient unit: Counts, step size: 0.02°, coefficient time: 20° / min) were performed on the yttrium oxide sample using an X-ray diffractometer (product name: Ultima IV, manufactured by Rigaku Corporation). The measurement data was read using the analysis software PDXL (manufactured by Rigaku Corporation) which uses the fundamental parameter method, and the XRD pattern of the crystal structure model was simulated using the ICDD database. The measured XRD pattern and the XRD pattern obtained from the crystal structure model were fitted together, and the crystallite size of the sample was determined from the values ​​obtained using the Rietveld method, which optimizes the results using the least squares method to minimize the residuals. For the XRD data of yttrium oxide, ICDD card No. 01-089-05592 was used.

[0065] Measurement of 50% particle size (Dm) For the yttrium oxide sample, the volume-based particle size distribution was measured using a laser diffraction particle size distribution analyzer (product name: MASTER SIZER3000, manufactured by MALVERN), and the particle size corresponding to 50% of the cumulative size from the smallest diameter side was determined as Dm.

[0066] Measurement of BET specific surface area For the yttrium oxide sample, the BET specific surface area was measured using the BET method with a single-point method using nitrogen gas, employing an automated specific surface area analyzer (product name: Macsorb, manufactured by Mountec Co., Ltd.).

[0067] [Table 1]

[0068] Example 1 Yttrium-4 oxide (Y2O3) and yttrium fluoride (YF3), obtained by heat treatment, with a crystallite size of 328.6 nm, were used. Lanthanum nitride (LaN) was used as the La source, silicon nitride (Si3N4) as the Si source, and cerium fluoride (CeF3) as the Ce source. Each raw material was weighed so that the molar ratio of each element was La:Y:Si:Ce = 3.50:1.00:6.00:1.00. The molar ratio of Y2O3 to YF3 was 1:1. Specifically, 37.5 parts by mass of LaN, 4.0 parts by mass of Y2O3, 5.1 parts by mass of YF3, 19.7 parts by mass of Si3N4, and 13.8 parts by mass of CeF3 were weighed.

[0069] The weighed raw materials were thoroughly crushed and mixed dry to obtain a mixture (hereinafter also referred to as the raw material mixture). The obtained raw material mixture was packed into a crucible and heat-treated at 1500°C for 5 hours under a reducing atmosphere. At that time, the heating rate from room temperature to 1200°C was set to 300°C per hour (5°C / min), and the heating rate from 1200°C to 1500°C was set to 60°C per hour (1°C / min) to obtain a second heat-treated product. The obtained second heat-treated product was crushed and dispersed in water for 2 hours, and then the nitride phosphor was recovered by solid-liquid separation. The recovered nitride phosphor was stirred in a 7% by mass hydrochloric acid aqueous solution for 1 hour, washed with water until the pH was neutral at about 7.0, and then dried to obtain the nitride phosphor of Example 1 in powder form.

[0070] Comparative Example 1 The nitride phosphor of Comparative Example 1 was obtained using the same procedure as in Example 1, except that yttrium oxide 1, which has an untreated crystallite size of 148.8 nm, was used instead of yttrium oxide 4.

[0071] Comparative Example 2 The nitride phosphor of Comparative Example 2 was obtained using the same procedure as in Example 1, except that untreated yttrium oxide with a crystallite size of 90.5 nm was used instead of yttrium oxide 4.

[0072] Evaluation of luminescence characteristics For the nitride phosphors obtained above, relative emission intensity, chromaticity, emission peak wavelength, and full width at half maximum were measured using a quantum efficiency measurement system (QE-2000, manufactured by Otsuka Electronics Co., Ltd.) with an excitation light wavelength of 450 nm at room temperature (25°C). The results are shown in Table 2. The emission spectra are shown in Figure 3. The relative emission intensity in Table 2 was calculated using the emission intensity of the nitride phosphor of Comparative Example 1 as the reference (100.0%).

[0073] Evaluation of 50% particle size (Dm) For the nitride phosphors obtained above, the volume-based particle size distribution was measured using a laser diffraction particle size distribution analyzer (product name: MASTER SIZER3000, manufactured by MALVERN), and the particle size corresponding to 50% of the cumulative total from the smallest diameter side was determined as Dm. The results are shown in Table 2.

[0074] [Table 2]

[0075] Example 2 The nitride phosphor of Example 2 was obtained using the same procedure as in Example 1, except that the raw material mixture was prepared so that the molar ratio of each element was La:Y:Si:Ce = 3.20:0.90:6.00:0.80.

[0076] Comparative Example 3 Comparative Example 3's nitride phosphor was obtained using the same procedure as in Example 1, except that unheat-treated yttrium oxide (Y2O3) with a crystallite size of 53.2 nm was used, and the raw material mixture was prepared so that the molar ratio of each element was La:Y:Si:Ce = 3.20:0.90:6.00:0.80.

[0077] Evaluation of luminescence characteristics Relative emission intensity, chromaticity, emission peak wavelength, and full width at half maximum were measured in the same manner as described above. The results are shown in Table 3. The emission spectrum is shown in Figure 4. In Table 3, the relative emission intensity was calculated using the emission intensity of the nitride phosphor in Comparative Example 3 as the reference (100.0%).

[0078] [Table 3]

[0079] As shown in Tables 2 and 3, using heat-treated yttrium oxide as a raw material improves the emission intensity of the resulting nitride phosphor. Furthermore, Example 1, which has a higher yttrium ratio in the nitride phosphor composition, exhibits a longer emission peak wavelength and even greater emission intensity. Therefore, using heat-treated yttrium oxide as a raw material is more effective in the production of nitride phosphors that require longer wavelength components.

[0080] Example 3 As the first heat-treated material, yttrium-4 oxide (Y2O3) with a crystallite size of 328.6 nm obtained by heat treatment was used. Lanthanum nitride (LaN) was used as the La source, silicon nitride (Si3N4) as the Si source, and cerium fluoride (CeF3) as the Ce source. Each raw material was weighed so that the molar ratio of each element was La:Y:Si:Ce = 3.20:1.00:6.00:1.00. Specifically, 41.0 parts by mass of LaN, 18.9 parts by mass of Y2O3, 23.5 parts by mass of Si3N4, and 16.5 parts by mass of CeF3 were weighed.

[0081] The weighed raw materials were thoroughly crushed and mixed dry to obtain a raw material mixture. The obtained raw material mixture was packed into a crucible and heat-treated at 1300°C for 5 hours under a reducing atmosphere. After being removed from the crucible, it was thoroughly crushed and mixed dry again and heat-treated again at 1540°C for 10 hours under a reducing atmosphere. The obtained second heat-treated product was crushed and dispersed in water for 2 hours, after which the nitride phosphor was recovered by solid-liquid separation. The recovered nitride phosphor was stirred in a 7% by mass hydrochloric acid aqueous solution for 1 hour, washed with water until the pH became neutral at approximately 7.0, and then dried to obtain the nitride phosphor of Example 3 in powder form.

[0082] Example 4 The nitride phosphor of Example 4 was obtained using the same procedure as in Example 3, except that yttrium 5 oxide, which has a crystallite size of 292.8 nm, was used instead of yttrium 4 oxide.

[0083] Example 5 The nitride phosphor of Example 5 was obtained using the same procedure as in Example 3, except that yttrium oxide 6, which has a crystallite size of 491.9 nm, was used instead of yttrium oxide 4.

[0084] Comparative Example 4 The nitride phosphor of Comparative Example 4 was obtained using the same procedure as in Example 3, except that yttrium oxide 1, which has an untreated crystallite size of 148.8 nm, was used instead of yttrium oxide 4.

[0085] Evaluation of luminescence characteristics Relative emission intensity, chromaticity, emission peak wavelength, and full width at half maximum were measured in the same manner as described above. The results are shown in Table 4. The emission spectrum is shown in Figure 5. In Table 4, the relative emission intensity was calculated using the emission intensity of the nitride phosphor of Comparative Example 4 as the reference (100.0%).

[0086] [Table 4]

[0087] As shown in Table 4, even when the second heat treatment step is carried out in two stages at different temperatures, using heat-treated yttrium oxide as the raw material improves the luminescence intensity of the resulting nitride phosphor.

[0088] Example 6 Yttrium-4 oxide (Y2O3) and yttrium fluoride (YF3), obtained by heat treatment, with a crystallite size of 328.6 nm, were used. Lanthanum nitride (LaN) was used as the La source, silicon nitride (Si3N4) as the Si source, and cerium fluoride (CeF3) and cerium nitride (CeN) were used as the Ce source. Each raw material was weighed so that the molar ratio of each element was La:Y:Si:Ce = 3.20:1.00:6.00:1.00. The molar ratio of Y2O3 to YF3 was set to 1:1, and the molar ratio of CeF3 to CeN was also set to 1:1. Specifically, 38.2 parts by mass of LaN, 4.0 parts by mass of Y2O3, 5.2 parts by mass of YF3, 20.0 parts by mass of Si3N4, 7.0 parts by mass of CeF3, and 5.5 parts by mass of CeN were weighed.

[0089] The weighed raw materials were thoroughly crushed and mixed dry to obtain a raw material mixture. The obtained raw material mixture was packed into a crucible and heat-treated at 1525°C for 8 hours under a reducing atmosphere. During this process, the heating rate from room temperature to 1200°C was set to 300°C per hour (5°C / min), and the heating rate from 1200°C to 1525°C was set to 60°C per hour (1°C / min) to obtain a second heat-treated product. The obtained second heat-treated product was crushed and dispersed in water for 15 hours, after which the nitride phosphor was recovered by solid-liquid separation. The recovered nitride phosphor was stirred in a 7% by mass hydrochloric acid aqueous solution for 1 hour, then washed with water until the pH became neutral at approximately 7.0, and dried to obtain the nitride phosphor of Example 6 in powder form.

[0090] Example 7 The nitride phosphor of Example 7 was obtained using the same procedure as in Example 6, except that yttrium-6 oxide (Y2O3) with a crystallite size of 491.9 nm was used instead of yttrium-4 oxide.

[0091] Comparative Example 5 The nitride phosphor of Comparative Example 5 was obtained using the same procedure as in Example 6, except that untreated yttrium-1 oxide (Y2O3) with a crystallite size of 148.8 nm was used instead of yttrium-4 oxide.

[0092] Crystallite size measurement of nitride phosphors XRD measurements (X-ray Diffraction, CuKα, tube voltage: 40kV, tube current: 20mA, scanning range: within 10° to 70° (10°≦2θ≦70°), radiation source: CuKα, scanning axis: 2θ / θ, measurement method: FT, coefficient unit: Counts, step size: 0.02°, coefficient time: 20° / min) were performed on the nitride phosphors obtained above using an X-ray diffractometer (product name: Ultima IV, manufactured by Rigaku Corporation). The measurement data was read using the analysis software PDXL (manufactured by Rigaku Corporation) which uses the fundamental parameter method, and the XRD pattern of the crystal structure model was simulated using the ICDD database. The measured XRD pattern and the XRD pattern obtained from the crystal structure model were fitted, and the crystallite size of the sample was determined from the values ​​obtained using the Rietveld method, which optimizes the results using the least squares method to minimize the residuals. Note that XRD data for nitride phosphors can be found on ICDD card No. 01-083-8621 (Ce3Si6N 11 ) was used. The results are shown in Table 5.

[0093] Evaluation of luminescence characteristics Relative emission intensity, chromaticity, emission peak wavelength, and full width at half maximum were measured in the same manner as described above. The results are shown in Table 5. In Table 5, the relative emission intensity was calculated using the emission intensity of the nitride phosphor of Comparative Example 5 as the reference (100.0%).

[0094] [Table 5]

[0095] As shown in Table 5, the larger the crystallite size of yttrium oxide in the raw material, the higher the luminescence intensity. It is thought that the higher crystallinity of the rare earth compounds used as raw materials for nitride phosphors leads to better control of their reactivity as raw materials, resulting in higher luminescence intensity of the nitride phosphors. [Industrial applicability]

[0096] The nitride phosphors of this disclosure can be used, for example, as phosphors included in wavelength conversion members provided in light sources such as general lighting devices like ceiling lights, vehicle lighting devices like spotlights and headlamps, projection devices like projectors and head-up displays, imaging devices such as digital cameras, mobile phones and smartphones, monitors for personal computers (PCs), televisions, personal digital assistants (PDXs), smartphones, tablet PCs and mobile phones, and liquid crystal display devices.

Claims

1. Oxides containing yttrium (Y) ２ O ３ A compound containing ) is heat-treated at a temperature in the range of 1000°C to 1650°C to obtain a first heat-treated product having a crystallite size of 150 nm or more. The first heat-treated material contains a rare earth element M which is Y, and at least yttrium fluoride (YF ３ A source containing M, a source containing at least lanthanum nitride (LaN), and at least silicon nitride (Si ３ N ４ A Si source containing ) and at least cerium fluoride (CeF ３ The method includes a Ce source containing ), and a mixture prepared such that, when the raw materials contain 6 moles of Si, the ratio of moles of La is 2.0 or more and 4.0 or less, the ratio of moles of M is 0.3 or more and 1.2 or less, the ratio of moles of Ce is greater than 0 and 1.2 or less, the total ratio of moles of M and Ce is greater than 0.3 and less than 2.4, and the total ratio of moles of La, M and Ce is 3.2 or more and 5.8 or less, and the mixture is heat-treated at a temperature within the range of 1400°C to 1600°C to obtain a second heat-treated product, A method for producing a nitride phosphor having a nitride phosphor contained in the second heat-treated product having the composition shown in the following formula (2). L ｐ M ｑ Yes ６ N ｒ :Yes ｓ (2) (In equation (2) above, p, q, r, and s satisfy the following conditions: 2.0 ≤ p ≤ 2.7, 0.3 ≤ q ≤ 1.0, 10.5 ≤ r ≤ 11.5, 0 < s ≤ 1.0, 0.3 < (q + s) ≤ 2.0, and 2.95 ≤ p + q + s ≤ 3.

05. M is a rare earth element and contains at least Y.)

2. The method for producing a nitride phosphor according to claim 1, wherein the heat treatment temperature for obtaining the first heat-treated product is within the range of 1300°C to 1500°C.

3. The method for producing a nitride phosphor according to claim 1 or 2, wherein the first heat-treated product obtained has a crystallite size of 500 nm or less.

4. In obtaining the first heat-treated product, the first heat-treated product has a specific surface area of ​​0.5 m² as measured by the BET method. ２ / g or more 2.1m ２ A method for producing a nitride phosphor according to any one of claims 1 to 3, wherein the amount is less than or equal to / g.

5. A nitride phosphor having a crystallite size of 42 nm or less and a composition represented by the following formula (2). L ｐ M ｑ Yes ６ N ｒ :Yes ｓ (2) (In equation (2) above, p, q, r, and s satisfy the following conditions: 2.0 ≤ p ≤ 2.7, 0.3 ≤ q ≤ 1.0, 10.5 ≤ r ≤ 11.5, 0 < s ≤ 1.0, 0.3 < (q + s) ≤ 2.0, and 2.95 ≤ p + q + s ≤ 3.

05. M is a rare earth element and contains at least Y.)

6. The nitride phosphor according to claim 5, wherein the 50% particle size Dm corresponding to the cumulative 50% from the smallest diameter side in the volume-based particle size distribution is 10 μm or more and 50 μm or less.

7. A nitride phosphor according to claim 5 or 6, manufactured by the method for manufacturing a nitride phosphor according to any one of claims 1 to 4.

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