Phosphor powder, light-emitting agent for determining authenticity, authenticity determination method, and light-emitting device

Abstract

One aspect of the present disclosure provides a phosphor powder which contains a phosphor represented by the general formula (Sr1-xEux)3Li0.84yAl6.84+zSi14.16-zOzN28-z [in the general formula, x is at most 0.08, y is 0.02-2.00, and z is 0.50-1.80], and has a light emission peak in a wavelength range of 650-720 nm in fluorescent spectra obtained when radiating light having a wavelength of 450 nm.

Description

Phosphor powder, luminescent agent for authenticity determination, authenticity determination method, and luminescent device

[0001] The present disclosure relates to a phosphor powder, a luminescent agent for authenticity determination, an authenticity determination method, and a light-emitting device.

[0002] Light-emitting diodes (LEDs) using GaAs-based compound semiconductors such as GaInAs and InP-based compound semiconductors are known as light-emitting devices that emit near-infrared light. LEDs that emit near-infrared light are widely used in various remote control sensors, in-vehicle cameras, and the like. Furthermore, light in the near-infrared region has excellent biological permeability and is used in various fields such as medicine, agriculture, and food for quality inspection applications such as foreign object detection, and for measuring the concentrations of hemoglobin and oxygen in the blood. Near-infrared light can also be used as a heat source, and its applicability to measures such as preventing snow accumulation on LED traffic lights is also being considered.

[0003] The near-infrared light emitted from the above-mentioned LEDs has a sharp emission spectrum and a narrow half-width. Therefore, in fields where it is desirable to include various wavelength components, a light-emitting device that can extract light with a certain degree of broadness is desired.

[0004] As one of the candidates, phosphor powders that emit light including near-infrared light have been investigated (for example, Patent Documents 1 and 2). ６ｘ (Si, Al) ２７－１２ｘ (O, N) ３１－６ｘ Li ３ｙ , where 0.4≦x≦0.8, 0≦y≦0.35, and Sr ３ Si １２．４３２ Al ８．５６８ O １．６０８ N ２６．３９２ Li ０．９６ A phosphor containing an inorganic compound having a crystal having the same crystal structure as that of the above as a host crystal is disclosed.

[0005] The use of phosphor powder as a marker for determining authenticity to prevent counterfeiting of brand-name products and the like has also been considered (see, for example, Patent Document 4). In this case, the phosphor powder is used, for example, by being blended into ink for forming a latent mark to be affixed to genuine products.

[0006] JP 2020-041135 A JP 2020-188044 A International Publication No. 2022 / 244523 International Publication No. 2011 / 030747

[0007] One possible method for improving the luminescence intensity of phosphor powder is to increase the concentration of activator elements in the phosphor. However, it is known that increasing the concentration of activator elements leads to a significant decrease in luminescence intensity as the temperature during use of the phosphor increases, and this may not be useful. In the phosphor described in Patent Document 3, a tendency for luminescence intensity to improve by reducing the Li content has been shown. However, simply reducing the Li content shortens the peak wavelength of the phosphor, which also affects the luminescence wavelength. Therefore, the desired near-infrared emitting phosphor cannot be obtained by simply controlling the Li content.

[0008] The present disclosure aims to provide a phosphor powder that can exhibit excellent luminescence intensity when used at high temperatures (e.g., 200°C). The present disclosure also aims to provide a luminescent agent for authenticity determination that includes the above-mentioned phosphor powder, and an authenticity determination method. The present disclosure also aims to provide a light-emitting device that uses the above-mentioned phosphor powder.

[0009] The present disclosure provides the following [1] to [7].

[0010] [1] General formula (Sr １－ｘ EU ｘ ) ３ Li ０．８４ｙ Al ６．８４＋ｚ Si １４．１６－ｚ O ｚ N ２８－ｚ[2] A phosphor powder comprising a phosphor represented by the general formula [wherein x is 0.08 or less, y is 0.02 to 2.00, and z is 0.50 to 1.80], the phosphor powder having an emission peak in the wavelength region of 650 to 720 nm in a fluorescence spectrum obtained when irradiated with light having a wavelength of 450 nm. [3] The phosphor powder according to [1], wherein y is 0.08 to 0.30. [4] SrAlSi ４ N ７ [4] The phosphor powder according to [1] or [2], wherein the content of the crystalline phase represented by (Sr, Eu) when quantitatively analyzed by powder X-ray diffraction is 10 mass % or less. ３．６ LiAl ８ Si １１ O １０ N １９ (SiO) ０．４

[0013]

[0014] The phosphor powder according to any one of [1] to [3], wherein the content of a crystalline phase represented by the formula (I) is 10 mass % or less. [5] A luminescent agent for determining authenticity, comprising the phosphor powder according to any one of [1] to [4]. [6] A method for determining authenticity, comprising: providing a region containing a phosphor in at least a part of a product; irradiating the region with light having a wavelength of 450 nm; and determining the authenticity of the product based on the wavelength of the fluorescence emitted from the region, wherein the phosphor is the luminescent agent for determining authenticity according to [5]. [7] A light emitting device, comprising: a light emitting element that emits primary light; and a wavelength converter that absorbs a part of the primary light and emits secondary light having a wavelength longer than that of the primary light, wherein the wavelength converter comprises the phosphor powder according to any one of [1] to [4].

[0011] According to the present disclosure, it is possible to provide a phosphor powder that can exhibit excellent luminescence intensity when used at high temperatures (e.g., 200°C). According to the present disclosure, it is also possible to provide a luminescent agent for authenticity determination that includes the above-mentioned phosphor powder, and an authenticity determination method. According to the present disclosure, it is also possible to provide a light-emitting device that uses the above-mentioned phosphor powder.

[0012] Fig. 1 is a schematic cross-sectional view showing an example of a light emitting device, and Fig. 2 shows the emission spectrum at 200°C of the phosphor powder prepared in the example.

[0013] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

[0014] Unless otherwise specified, the materials exemplified in this specification can be used singly or in combination of two or more. When a plurality of substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified.

[0015] The phosphor powder according to one embodiment of the present disclosure is a phosphor represented by the general formula (Sr １－ｘ EU ｘ ) ３ Li ０．８４ｙ Al ６．８４＋ｚ Si １４．１６－ｚ O ｚ N ２８－ｚ The phosphor powder contains a phosphor represented by the general formula (1), wherein x is 0.08 or less, y is 0.02 to 2.00, and z is 0.50 to 1.80. The phosphor powder has an emission peak in the wavelength range of 650 to 720 nm in the fluorescence spectrum obtained when irradiated with light having a wavelength of 450 nm. The phosphor powder may contain a heterophase within the scope of the present invention, or may be a powder consisting of particles of the above-mentioned phosphor.

[0016] The phosphor powder contains Sr ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ It can also be said that the phosphor includes a host crystal having the same crystal structure as that of the phosphor shown in FIG. 1 and europium that is substituted into the host crystal and dissolved therein.

[0017] The phosphor powder described above maintains a low proportion of europium (Eu) in the phosphor while adjusting the proportions of lithium (Li) and oxygen (O) within the above-mentioned ranges, thereby suppressing the decrease in luminescence intensity during use at high temperatures and providing a phosphor with an emission peak wavelength in the near-infrared wavelength range that exhibits excellent luminescence intensity even at 200° C. The reason for the above-mentioned effect is not clear, but by adjusting the Li content to increase the Li content and the O content to decrease the O content, which were thought to result in longer wavelengths, it is possible to provide an unexpected effect of maintaining the wavelength in the near-infrared range while providing excellent luminescence intensity at high temperatures.

[0018] The upper limit of the value of x in the general formula may be, for example, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, or 0.03 or less. When the upper limit of the value of x is within the above range, a decrease in luminescence intensity during use at high temperatures can be more sufficiently suppressed. The lower limit of the value of x in the general formula may be, for example, 0.009 or more, 0.01 or more, 0.015 or more, 0.02 or more, or 0.021 or more. When the lower limit of the value of x is within the above range, better luminescence intensity can be exhibited during use at high temperatures. The value of x in the general formula may be adjusted within the above range, and may be, for example, 0.01 to 0.05, 0.02 to 0.05, or 0.02 to 0.03.

[0019] The upper limit of the value of y in the general formula may be, for example, 1.50 or less, 1.30 or less, 1.10 or less, 1.00 or less, 0.80 or less, 0.70 or less, 0.65 or less, 0.62 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.35 or less, 0.30 or less, 0.29 or less, 0.28 or less, 0.27 or less, 0.26 or less, 0.25 or less, 0.24 or less, 0.23 or less, or 0.22 or less. By setting the upper limit of the value of y within the above range, it is possible to further suppress the generation of defects due to the excessive addition of Li to the crystal structure, and it is possible to further increase the luminescence intensity. The lower limit of the value of y in the above general formula may be, for example, 0.02 or more, 0.10 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, 0.19 or more, 0.20 or more, or 0.21 or more. By setting the lower limit of the value of y within the above range, the obtained phosphor powder can exhibit superior luminescence intensity when used at high temperatures. The value of y in the above general formula may be adjusted within the above range, and may be, for example, 0.02 to 1.30, 0.02 to 1.00, 0.02 to 0.80, 0.08 to 0.30, 0.10 to 0.70, 0.14 to 0.60, 0.15 to 0.50, 0.16 to 0.40, 0.17 to 0.30, 0.18 to 0.28, 0.19 to 0.26, 0.20 to 0.24, or 0.21 to 0.22.

[0020] The value of z in the above general formula is Sr ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２The formula is based on an inorganic crystal represented by the formula (I), and the ratio of O is adjusted to be lower than the ratio of oxygen (O). The upper limit of the value of z in the general formula may be, for example, 1.75 or less, 1.73 or less, or 1.70 or less. By setting the upper limit of the value of z within the above range, the luminescence intensity can be further increased. Furthermore, by adjusting the blending ratio of oxygen in the raw material mixture to produce such a phosphor powder, the ratio of heterophases in the phosphor powder can be reduced. The lower limit of the value of z in the general formula may be, for example, 0.10 or more, 1.10 or more, 1.20 or more, 1.30 or more, 1.40 or more, 1.50 or more, or 1.60 or more. By setting the lower limit of the value of z within the above range, oxygen site deficiencies in the crystal structure can be further suppressed, further increasing the luminescence intensity at high temperatures. The value of z in the general formula may be adjusted within the above range, for example, 1.40 to 1.75, 1.50 to 1.75, or 1.60 to 1.73.

[0021] The constituent elements and ratios of the phosphor powder can be determined by an ICP optical emission spectroscopy method using an oxygen / nitrogen analyzer and a multi-type ICP optical emission spectroscopy analyzer. The ratios of O and N among the constituent elements of the phosphor powder can be determined using an oxygen / nitrogen analyzer. As an oxygen / nitrogen analyzer, the "EMGA-920" (trade name) manufactured by Horiba, Ltd. can be used. Note that the elemental composition of a phosphor corresponds to the ratio of each element charged when the phosphor is manufactured, so the elemental composition of the phosphor can also be estimated from the raw material composition.

[0022] The phosphor is Sr ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ It has the same crystal structure as

[0023] The phosphor is Sr ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２It can be confirmed by powder X-ray diffraction measurement whether the phosphor has the same crystal structure as Sr. More specifically, in a diffraction pattern (a graph in which the horizontal axis represents the diffraction angle 2θ [unit: °] and the vertical axis represents the diffraction intensity [unit: CPS]) obtained by powder X-ray diffraction measurement of the phosphor to be measured, ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ This can be determined by the diffraction pattern obtained by powder X-ray diffraction measurement and whether or not a major peak is observed. ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ The diffraction pattern obtained by powder X-ray diffraction measurement of the compound of formula (I) shows major peaks at 34.4°, 28.2°, 30.8°, and 33.8°.

[0024] The phosphor may belong to the hexagonal crystal system and have a space group of P6 ３ The crystal may have a symmetrical space group corresponding to number 173 in the International Tables for Crystallography.

[0025] In this specification, the space group of a crystal is determined by comparing the diffraction pattern of the X-ray diffraction spectrum of the sample to be measured with the diffraction pattern of a crystal group with a defined symmetry.

[0026] The phosphor may be prepared so that the lattice constants a, b, and c measured by powder X-ray diffraction are within a predetermined range. Here, the lattice constants a, b, and c refer to the a-axis length, b-axis length, and c-axis length of the crystal lattice constituting the phosphor, respectively. The lattice constants a, b, and c of the phosphor may be 1.6 nm < a < 1.8 nm, b = a, and 0.44 nm < c < 0.52 nm, respectively.

[0027] Although the phosphor powder may contain a different phase, it is desirable that the content of the different crystalline phase be kept appropriately low.３ (Si, Al) １９ (O, N) ２９ ]Sr ０．５９ [(Si,Al)(O,N)] ０．４１ The crystalline phase (heterogeneous phase 1) represented by SrAlSi ４ N ７ A crystalline phase (heterogeneous phase 2) represented by Sr ２ Si ５ N ８ A crystalline phase (heterogeneous phase 3) represented by (Sr, Eu) ３．６ LiAl ８ Si １１ O １０ N １９ (SiO) ０．４ These heterophases can absorb light irradiated to excite the phosphor represented by the general formula above, and therefore, by reducing the content of the heterophase crystalline phase, the luminescence intensity of near-infrared light emitted from the phosphor powder can be further increased.

[0028] The phosphor powder was quantitatively analyzed by powder X-ray diffraction to determine the content of [LiSr ３ (Si, Al) １９ (O, N) ２９ ]Sr ０．５９ [(Si,Al)(O,N)] ０．４１The content of the crystalline phase (heterophase 1) represented by the formula (I) may be, for example, 10% by mass or less, 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, or 5% by mass or less, where the total amount of crystalline components detected by quantitative analysis using powder X-ray diffraction is taken as 100% by mass. The phosphor powder can further increase its luminescence intensity at high temperatures (e.g., 200°C) by containing heterophase 1. The reason for this effect is unclear, but the effect of increasing luminescence intensity by the presence of a trace amount of a specific heterophase, even though it is generally considered preferable to have no heterophase, is unexpected. The content of the heterophase 1 in the phosphor powder when quantitatively analyzed using powder X-ray diffraction may be, for example, 1% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or more, where the total amount of crystalline components detected by quantitative analysis using powder X-ray diffraction is taken as 100% by mass. The content of the heterophase 1 may be adjusted within the above range, and may be, for example, 1 to 5 mass%, 3 to 5 mass%, or 4 to 5 mass%, where the total amount of crystalline components detected by quantitative analysis using powder X-ray diffraction is 100 mass%.

[0029] The phosphor powder was found to be SrAlSi when quantitatively analyzed by powder X-ray diffraction. ４ N ７ The content of the crystalline phase (heterophase 2) represented by the formula (I) may be, for example, 10% by mass or less, 9% by mass or less, 8% by mass or less, or 7% by mass or less, where the total amount of crystalline components detected by quantitative analysis using powder X-ray diffraction is 100% by mass, and the heterophase 2 may not be contained.

[0030] The phosphor powder was found to contain Sr when quantitatively analyzed by powder X-ray diffraction. ２ Si ５ N ８ The content of the crystalline phase (heterophase 3) represented by the formula (I) may be, for example, 10% by mass or less, 9% by mass or less, 8% by mass or less, or 7% by mass or less, where the total amount of crystalline components detected by quantitative analysis using powder X-ray diffraction is 100% by mass, and the heterophase 3 may not be contained.

[0031] The phosphor powder was found to have a composition of (SrEu) when quantitatively analyzed by powder X-ray diffraction. ３．６ LiAl ８ Si１１ O １０ N １９ (SiO) ０．４ The content of the crystalline phase (heterophase 4) represented by the formula (I) may be, for example, 10% by mass or less, 9% by mass or less, 8% by mass or less, or 7% by mass or less, where the total amount of crystalline components detected by quantitative analysis using powder X-ray diffraction is 100% by mass, and the heterophase 4 may not be contained.

[0032] The proportion of the phosphor represented by the general formula above and the proportions of various heterophases in the phosphor powder can be determined by analyzing the X-ray powder diffraction pattern by the Rietveld method. The Rietveld analysis can be performed using, for example, the integrated powder X-ray analysis software "PDXL" manufactured by Rigaku Holdings Corporation.

[0033] When the phosphor powder contains heterophase 1, the content of heterophase 1 in the phosphor powder may be, for example, 4 to 5 mass % where the total amount of crystalline components detected by quantitative analysis using powder X-ray diffraction is 100 mass %, and x in the general formula may be 0.02 to 0.03, y may be 0.17 to 0.30, and z may be 1.60 to 1.73. In this case, it is desirable that the phosphor powder does not contain either heterophase 2 or heterophase 3.

[0034] The emission peak wavelength of the phosphor powder depends on the amount of Eu dissolved in the solid solution and the proportion of Eu in the solid solution element. ２＋The ratio of the phosphor to the total phosphor content can be adjusted by, for example, adjusting the ratio of the phosphor to the total phosphor content. In the fluorescence spectrum obtained when irradiated with light having a wavelength of 450 nm, the phosphor may have an emission peak in the wavelength range of 650 to 720 nm. In the fluorescence spectrum obtained when irradiated with light having a wavelength of 450 nm, the emission peak wavelength having the maximum emission intensity of the phosphor powder in the wavelength range of 650 to 720 nm can be, for example, 660 nm or more, 670 nm or more, 680 nm or more, 690 nm or more, or 700 nm or more. The emission peak wavelength having the maximum emission intensity of the phosphor powder can be, for example, 750 nm or less, 740 nm or less, 730 nm or less, 720 nm or less, 710 nm or less, or 705 nm or less. The emission peak wavelength may be adjusted within the above-mentioned range, and may be, for example, 700 to 710 nm or 700 to 705 nm.

[0035] In this specification, the emission peak wavelength of a phosphor is a value determined by measuring the emission spectrum when irradiated with light having a wavelength of 450 nm, and refers to the emission peak wavelength having the maximum emission intensity. The emission spectrum measurement is performed on the phosphor powder to be measured.

[0036] An example of a method for producing a phosphor powder includes calcining a raw material mixture containing a strontium source, a europium source, a lithium source, an aluminum source, and a silicon source under an inert gas atmosphere to obtain a calcined product (hereinafter also referred to as a calcination step). １－ｘ EU ｘ ) ３ Li ０．８４ｙ Al ６．８４＋ｚ Si １４．１６－ｚ O ｚ N ２８－ｚ The fired product contains a phosphor represented by the general formula (wherein x is 0.08 or less, y is 0.02 to 2.00, and z is 0.50 to 1.80), and the amount of lithium in the raw material mixture is three times or more the Li content (0.84y) in the general formula.

[0037] The strontium source, europium source, lithium source, aluminum source, and silicon source may be oxides, nitrides, or carbonates independently of one another, but at least one of them is a nitride.

[0038] The lower limit of the amount of lithium (Li) in the raw material mixture is 3 times or more, but may be, for example, 4 times or more, 5 times or more, or 6 times or more, based on the Li content of 0.84y in the general formula. By setting the lower limit of the amount of lithium in the raw material mixture within the above range, the luminescence intensity of the resulting phosphor powder when used at high temperatures can be further increased. The upper limit of the amount of lithium in the raw material mixture may be, for example, 9 times or less, 8 times or less, or 7 times or less, based on the Li content of 0.84y in the general formula. By setting the upper limit of the amount of lithium in the above range, excessive addition of lithium atoms to the crystal structure can be more sufficiently suppressed, and the luminescence intensity can be further improved.

[0039] The amount of oxygen (O) in the raw material mixture is determined by the amount of Sr ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ The oxygen content may be adjusted to be 0.30 times or more of 1.608, assuming an O content (element ratio) of 1.608 as a reference. The lower limit of the oxygen content in the raw material mixture may be, for example, 0.30 times or more, 0.40 times or more, 0.50 times or more, or 0.62 times or more. By setting the lower limit of the oxygen content within the above range, oxygen atom deficiency in the crystal structure can be further suppressed, and the luminescence intensity during high-temperature use can be further improved. The upper limit of the oxygen content in the raw material mixture may be, for example, 1.30 times or less, 1.25 times or less, 1.20 times or less, 1.00 times or less, or 0.80 times or less. By setting the upper limit of the oxygen content within the above range, heterophases (particularly, (SrEu) ３．６ LiAl ８ Si １１ O １０ N １９ (SiO) ０．４The proportion of the crystalline phase represented by the formula (II) can be more sufficiently reduced, and the luminescence intensity of the phosphor powder can be further improved.

[0040] The raw material mixture can be prepared by weighing and mixing each compound. A dry mixing method or a wet mixing method may be used for mixing. The dry mixing method may be, for example, a method in which each component is mixed using a V-type mixer or the like. The wet mixing method may be, for example, a method in which a solvent or dispersion medium such as water is added to prepare a solution or slurry, the components are mixed, and then the solvent or dispersion medium is removed.

[0041] The inert gas atmosphere may be an atmosphere containing nitrogen or may be an atmosphere consisting of nitrogen.

[0042] The heating temperature (firing temperature) in the firing step may be, for example, 1000 to 2200°C, 1500 to 2100°C, 1800 to 2100°C, or 1900 to 2000°C. When the lower limit of the firing temperature is within the above range, the reaction can be further promoted. Furthermore, when the upper limit of the firing temperature is within the above range, the decomposition and volatilization of the raw material components can be further suppressed.

[0043] The heating time (firing time) in the firing step may be, for example, 1 to 30 hours, 2 to 15 hours, or 3 to 9 hours.

[0044] The above-described production method may include other steps in addition to the firing step, such as a crushing step and a classification step.

[0045] In this specification, the heating time such as the firing time means the time (retention time) during which the temperature of the environment surrounding the object is maintained at a predetermined temperature after the temperature reaches that temperature.

[0046] The crushing step is a step in which the fired product obtained in the firing step and the heat-treated product obtained in the reduction step are crushed to adjust the particle size, since they may be obtained in lumps. In the crushing step, a mortar or a mortar may be used, or a general crusher or crusher may be used. Examples of crushers and crushers include a ball mill, a jet mill, and a Henschel mixer. The crushing step is preferably performed by wet ball mill crushing in the presence of a medium such as ion-exchanged water. Zirconia balls may be used in the ball mill.

[0047] One embodiment of the luminescent agent for authenticity determination includes the above-described phosphor powder. Since the above-described phosphor powder can be used as a near-infrared emitting phosphor, it can be used as a marker for authenticity determination while suppressing emission in the visible light region. The luminescent agent for authenticity determination can be used to determine authenticity based on the emission wavelength obtained when irradiated with light having a wavelength of 450 nm.

[0048] One embodiment of the authentication method includes providing a region containing a phosphor in at least a portion of a product, irradiating the region with light having a wavelength of 450 nm, and determining the authenticity of the product based on the wavelength of fluorescence emitted from the region. The phosphor is the above-mentioned luminescent agent for authenticity determination. Information on the emission wavelength obtained when irradiated with light having a wavelength of 450 nm is acquired in advance, and if a fluorescent wavelength matching this information is acquired, the product having the region can be determined to be authentic. In addition to the wavelength of the fluorescence, for example, the shape of the fluorescence spectrum can also be used as a judgment factor for the above-mentioned authenticity determination, and the authenticity may be determined based on the wavelength and shape of the fluorescence spectrum acquired in advance. In this case, the above-mentioned determination method can also be said to determine the authenticity of the product based on the wavelength and shape of the fluorescence spectrum of the fluorescence emitted from the region.

[0049] An example of a light emitting device is a light emitting device including a light emitting element that emits primary light and a wavelength converter that absorbs a part of the primary light and emits secondary light having a wavelength longer than that of the primary light. The wavelength converter contains the phosphor powder described above. The light emitting element and the wavelength converter may be sealed with a sealing resin or the like.

[0050] FIG. 1 is a schematic cross-sectional view showing an example of a light-emitting device. The light-emitting device shown in FIG. 1 is an example of an optical semiconductor device classified as a surface-mount type. The light-emitting device 100 includes a substrate 10, a light-emitting element 40 electrically connected to a metal layer 20 provided on the surface of the substrate 10, a reflector 30 provided on the surface of the substrate 10 so as to surround the light-emitting element 40, and a transparent sealing resin 60 filled in a recess formed by the substrate 10 and the reflector 30 to seal the light-emitting element 40. A near-infrared light-emitting phosphor 52 and other phosphors 54 are dispersed in the transparent sealing resin 60. The near-infrared light-emitting phosphor 52 includes the phosphor powder according to the present disclosure. Note that while FIG. 1 shows an example in which the other phosphor 54 is included, an embodiment in which the other phosphor 54 is not included is also possible.

[0051] The substrate 10 has a metal layer 20 formed on a portion of its surface, and the metal layer 20 serves as an electrode that is electrically connected to a light-emitting element 40 arranged on the surface of the substrate 10. The light-emitting element 40 is die-bonded to the metal layer 20 on either the anode side or the cathode side, and is electrically connected to the metal layer 20 via a die-bonding material 42. The light-emitting element 40 is electrically connected to the metal layer 20 on either the anode side or the cathode side via a bonding wire 44.

[0052] The reflecting portion 30 is filled with a transparent sealing resin 60 for sealing the light-emitting element 40, and reflects the light (excitation light) emitted from the light-emitting element 40, as well as the fluorescence emitted from the near-infrared light-emitting phosphor 52 and other phosphors 54 in response to the light, toward the surface side of the light-emitting device 100.

[0053] The light-emitting element 40 may emit light (primary light, excitation light) that can excite the near-infrared light-emitting phosphor 52 and the other phosphors 54. The light-emitting element 40 may be, for example, a near-ultraviolet light-emitting diode (near-ultraviolet LED), an ultraviolet light-emitting diode (ultraviolet LED), a blue light-emitting diode (blue LED), or the like. A plurality of light-emitting elements 40 may be provided.

[0054] The light emitting device 100 includes other phosphors 54 in addition to the near-infrared light emitting phosphor 52, but may include only the near-infrared light emitting phosphor 52. The other phosphors 54 may include, for example, a red phosphor, a yellow phosphor, a green phosphor, a blue phosphor, and the like.

[0055] In the above example, the light emitting device has been described as an optical semiconductor device classified as a surface mount type, but the light emitting device is not limited to this. The light emitting device is suitable for, for example, a light source for a spectroscopic analyzer, an infrared sensor for security, a food analyzer, a moisture measuring device, a gas detector, and a wearable device.

[0056] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. Furthermore, the descriptions of the above embodiments can be applied to each other.

[0057] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0058] Example 1 Strontium nitride (Sr ３ N ２ , manufactured by Materion) 2.311 g, europium oxide (Eu ２ O ３ , manufactured by Shin-Etsu Chemical Co., Ltd.) 0.042 g, lithium nitride (Li ３ 0.235 g of aluminum nitride (AlN, manufactured by Materion Corporation), 2.579 g of silicon nitride (Si ３ N ４ , manufactured by Ube Industries, Ltd.) 4.757 g, silicon dioxide (SiO ２ 0.234 g of each of the lithium (Li) compounds was weighed out and mixed in an alumina mortar under a nitrogen atmosphere for 10 minutes to obtain a raw material mixture. １－ｘ EU ｘ ) ３ Li ０．８４ｙ Al ６．８４＋ｚ Si １４．１６－ｚ O ｚ N ２８－ｚThe amount of Li in the raw material mixture was adjusted to be three times that of 0.84a, based on the Li compounding ratio (element ratio) of 0.84y (y = 3 in Example 1), which is assumed to be 0.84a. The amount of oxygen (O) in the raw material mixture was adjusted to be three times that of 0.84a. ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ Based on an assumed O compounding ratio (element ratio) of 1.608 as a standard, the amount of O compounded in the raw material mixture was adjusted to be 0.62 times 1.608.

[0059] Next, 5 g of the obtained raw material mixture was placed in an alumina crucible and placed in a vertical furnace. The temperature was increased from room temperature to 1900°C at a rate of 10°C / min and maintained at 1900°C for 4 hours. The atmosphere in the vertical furnace was kept as a nitrogen atmosphere. After that, the mixture was cooled to room temperature and crushed in an alumina mortar to obtain a fired powder.

[0060] The powder obtained as described above was (Sr １－ｘ EU ｘ ) ３ Li ０．８４ｙ Al ６．８４＋ｚ Si １４．１６－ｚ O ｚ N ２８－ｚ The composition was confirmed by the following composition analysis.

[0061] [Composition Analysis: Oxygen / Nitrogen Analysis and ICP Emission Spectroscopic Analysis] First, the oxygen and nitrogen contents were determined using an oxygen / nitrogen analyzer (manufactured by Horiba, Ltd., product name: EMGA-920). Measurements were performed by placing the phosphor to be measured in a graphite crucible, heating it to 280°C to remove surface adsorbates, and then increasing the temperature to 2400°C. The background oxygen content, which was previously measured under the same conditions in an empty graphite crucible, was subtracted from the measured oxygen content to obtain the oxygen and nitrogen contents in the fired body. Furthermore, the composition was analyzed using a multi-type ICP emission spectroscopic analyzer (manufactured by Agilent, model number: 5110VDV). 10 mg of the powder to be measured was placed in a platinum crucible, 2 g of alkaline flux was added, and the mixture was melted in an electric furnace. After cooling, 20 mL of hydrochloric acid (HCl) was added to the platinum crucible, and the mixture was dissolved by heating in a warm bath to obtain a solution. The resulting solution was then adjusted to a constant volume of 100 mL, and this 100 mL solution was diluted 10 times with pure water to prepare a test solution, which was then placed in the above-mentioned apparatus and its composition was analyzed.

[0062] (Examples 2 to 8, Comparative Examples 1 to 3) Phosphor powders were prepared in the same manner as in Example 1, except that the design composition, the amount of Li (lithium) blended in the raw material mixture, and the amount of O (oxygen) blended were changed as shown in Tables 1 and 2. The obtained phosphor powders were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2 and FIG. 2. The phosphor powder prepared in Comparative Example 1 had many heterophases, and Sr ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ The emission intensity derived from the phosphor having the same crystal structure as that of the compound (I) could not be identified, and is therefore indicated as "-" in Table 2.

[0063] [Confirmation of Crystal Structure] The crystal structure of the powders prepared in the examples and comparative example 2 was confirmed. First, the X-ray diffraction spectrum obtained in the examples was obtained. The obtained diffraction patterns were analyzed to determine the crystal structure of Sr ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ By comparing the X-ray diffraction pattern of the powder obtained in the example with that of the powder obtained in the example, it can be seen that the powder obtained in the example３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ It was confirmed that the powder prepared in Comparative Example 1 had the same crystal structure as Sr. The measurement was performed using an "Ultima IV" (product name) manufactured by Rigaku Corporation, with the measurement range set to 10 to 60°. ３ Li ０．９６ Al ８．５８６ Si １２．４３２ O １．６０８ N ２６．３９２ Although it was confirmed that a crystalline component having the same crystal structure as that of the powder was present, it could not be said that the main component in the powder was the crystalline component.

[0064] [Determination of the content of heterogeneous phases in phosphor powder] The powders prepared in the examples and comparative examples were analyzed to determine the content of heterogeneous phases in phosphor powders having the above general formula, [LiSr ３ (Si, Al) １９ (O, N) ２９ ]Sr ０．５９ [(Si,Al)(O,N)] ０．４１ (different phase 1), SrAlSi ４ N ７ (heterophase 2), and Sr ２ Si ５ N ８ The content of each of the crystalline phases represented by (heterophase 3) was determined. Specifically, the content of each phase was determined by analyzing the X-ray powder diffraction pattern using the Rietveld method. The Rietveld analysis was performed using the integrated powder X-ray analysis software "PDXL" manufactured by Rigaku Holdings Corporation. The results are shown in Tables 1 and 2.

[0065] [Determination of Emission Peak Wavelength] The emission intensity of the powders prepared in the Examples and Comparative Examples was measured to confirm their function as phosphors. First, the phosphor to be measured was filled into a quartz cell, which was then fixed in the attached fixed sample holder. Next, the emission spectrum was measured using light with a wavelength of 450 nm as excitation light. When measuring the excitation spectrum, the fluorescence monitor wavelength was used as the peak wavelength of the emission spectrum. The emission peak wavelength was also determined from the obtained emission spectrum. The emission spectrum was acquired at a temperature of 25°C (room temperature). A spectrofluorometer "Fluorolog-3-iHR-NIR" (product name) manufactured by Horiba, Ltd. was used for the measurement. The results are shown in Tables 1 and 2. For reference, the emission spectra of the powders prepared in Examples 1, 4, and 8, and Comparative Example 3 are shown in Figure 2.

[0066] [Evaluation of Emission Intensity at 200°C] The emission intensities at 200°C were evaluated for the powders prepared in the Examples and Comparative Examples. Specifically, an upright microscope manufactured by Olympus Corporation, a multichannel spectrometer MCPD-9800 3095 manufactured by Otsuka Electronics Co., Ltd., a blue laser light source (peak wavelength 452 nm) manufactured by Sawaki Kobo Co., Ltd., and a temperature characteristic evaluation stage HFS600 manufactured by Linkam Corporation (equipped with a heater for heating and a water cooling mechanism for cooling) were combined to obtain emission spectra. The measurement temperature was 200°C, and the emission intensities at 200°C were obtained. Note that the emission intensities in Tables 1 and 2 are relative values, with the emission intensity of the phosphor powder of Example 2 set to 100.

[0067]

[0068]

[0069] As shown in Tables 1 and 2, it was confirmed that the phosphor powders prepared in Examples 1 to 8 exhibited relatively high luminous intensity even at 200°C.

[0070] According to the present disclosure, it is possible to provide a phosphor powder that can exhibit excellent luminescence intensity when used at high temperatures (e.g., 200° C.). According to the present disclosure, it is also possible to provide a luminescent agent for authenticity determination, and an authenticity determination method, which include the above-mentioned phosphor powder.

[0071] 10...base material, 20...metal layer, 30...reflecting portion, 40...light emitting element, 42...die bond material, 44...bonding wire, 52...near-infrared emitting phosphor, 54...other phosphor, 60...transparent sealing resin, 100...light emitting device

Claims

1. General formula (Sr １－ｘ EU ｘ ) ３ Li ０．８４ｙ Al ６．８４＋ｚ Si １４．１６－ｚ O ｚ N ２８－ｚ [In the general formula, x is 0.08 or less, y is 0.02 to 2.00, and z is 0.50 to 1.80], the phosphor powder having an emission peak in a wavelength region of 650 to 720 nm in a fluorescence spectrum obtained when irradiated with light having a wavelength of 450 nm.

2. The phosphor powder according to claim 1, wherein y is 0.08 to 0.

30.

3. SrAlSi ４ N ７ 3. The phosphor powder according to claim 1, wherein the content of the crystalline phase represented by the formula (I) is 10 mass % or less.

4. (Sr, Eu) when quantitatively analyzed by powder X-ray diffraction ３．６ LiAl ８ Si １１ O １０ N １９ (SiO) ０．４ 3. The phosphor powder according to claim 1, wherein the content of the crystalline phase represented by the formula (I) is 10 mass % or less.

5. A luminescent agent for determining authenticity, comprising the phosphor powder according to claim 1 or 2.

6. A method of determining authenticity, comprising providing an area containing a fluorescent substance in at least a part of a product, irradiating said area with light having a wavelength of 450 nm, and determining the authenticity of said product based on the wavelength of the fluorescence emitted from said area, wherein said fluorescent substance is the luminescent agent for determining authenticity as described in claim 5.

7. A light emitting device comprising a light emitting element that emits primary light and a wavelength converter that absorbs a portion of the primary light and emits secondary light having a wavelength longer than that of the primary light, wherein the wavelength converter contains the phosphor powder according to claim 1 or 2.

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