Phosphor and ink composition

Abstract

One aspect of the present disclosure provides a phosphor which is represented by general formula (Eu(1 - x)(1 - y)LaxM(1 - x)z)2(Si(1 - y)Aly)5N8, wherein when D97 is the 97% cumulative diameter in the volume-based cumulative particle size distribution, D97 is 8.50 μm or less. In the general formula, M represents Ba, or two or more elements that are Ba and one or more elements selected from the group consisting of Mg, Ca, and Sr, x represents a numerical value of 0.05 or more and 0.20 or less, y represents a numerical value of 0.00 or more and 0.10 or less, z represents a numerical value of more than 0.44 and not more than 0.80, and (1 - x)z is less than 0.70.

Description

Fluorescent material and ink composition

[0001] The present disclosure relates to phosphors and ink compositions.

[0002] Fluorescent materials that emit near-infrared light have attracted attention. For example, light-emitting diodes that emit near-infrared light are widely used in various remote control sensors, in-vehicle cameras, etc. 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 detecting foreign objects, and for measuring the concentrations of hemoglobin and oxygen in blood.

[0003] Since near-infrared light-emitting phosphors do not emit light in the visible region and are therefore not visible to the naked eye, their use in security applications has also been considered. For security applications, their use in forming markers for determining authenticity to prevent counterfeiting of brand-name products and the like has been considered (see, for example, Patent Document 1). In this case, the phosphors are used, for example, by being blended into ink (security ink) for forming latent marks to be affixed to genuine products.

[0004] Various phosphors that emit near-infrared light have been studied (for example, Patent Documents 1 to 4). Patent Document 4 describes a phosphor having the general formula: (Eu(1-x)(1-y)M1 ｘ M2 （１－ｘ）ｚ ) ２ (Si （１－ｙ） Al ｙ ) ５ N ８ The patent document discloses a powder containing a phosphor represented by the formula: M1 contains at least La, and further contains one or more elements selected from the group consisting of Y and lanthanoid elements other than La. M2 also contains at least Ba, and further contains one or more elements selected from the group consisting of Mg, Ca, and Sr.

[0005] International Publication No. 2011 / 030747 Japanese Patent Application Laid-Open No. 2020-041135 Japanese Patent Application Laid-Open No. 2020-188044 International Publication No. 2022 / 186069

[0006] The near-infrared phosphor used in security ink is required to emit no fluorescence other than the desired near-infrared emission, or at least to have low emission intensity of fluorescence (sub-peaks) in the visible region other than the intended region, and to have a small particle size for printing by inkjet or the like.

[0007] The present disclosure aims to provide a near-infrared phosphor having reduced sub-peak intensities, and also to provide an ink composition containing the near-infrared phosphor.

[0008] Through research by the present inventors, we attempted to reduce the particle size of the phosphor powder described in Patent Document 4 for use in security ink, and discovered a new finding: the smaller the particle size, the greater the fluorescent emission intensity in the visible region. The phosphor powder disclosed in Patent Document 3, when it does not contain lanthanum (La), emits red light around 660 nm. However, the introduction of La induces distortion in the crystalline structure constituting the phosphor, and the red light is absorbed in the distorted areas, resulting in a phosphor that emits new near-infrared fluorescence. While the reason for the increased visible light intensity associated with reduced particle size in the La-introduced phosphor is unclear, the applicant speculates as follows: In other words, when the particle size is large, the red light travels a considerable distance before escaping from the phosphor particles, increasing the probability that it will be absorbed by the distorted areas during this distance. Therefore, it is believed that the red light component (subpeak) in the phosphor powder as a whole is reduced during emission. On the other hand, the applicant presumes that as the particle size of the phosphor particles becomes smaller, the red emission is absorbed and emitted to the outside without wavelength conversion, resulting in an increase in the emission intensity in the visible region. Furthermore, the applicant has found that by increasing the La content, the amount of distortion in the crystal structure increases, thereby increasing the probability of absorbing the red emission, and thereby suppressing the emission in the visible region even when the particle size is reduced. The present disclosure has been made based on the above-mentioned findings.

[0009] One aspect of the present disclosure provides, for example, a phosphor represented by the following formula [1]: [1] General formula: (Eu(1-x)(1-y)Laｘ M （１－ｘ）ｚ ) ２ (Si （１－ｙ） Al ｙ ) ５ N ８ A phosphor represented by the formula: wherein, in said general formula, M represents Ba, or two or more elements of Ba and one or more elements selected from the group consisting of Mg, Ca, and Sr, x represents a numerical value of 0.05 or more and 0.20 or less, y represents a numerical value of 0.00 or more and 0.10 or less, z represents a numerical value of more than 0.44 and 0.80 or less, and (1-x)z is less than 0.70, and when D97 is defined as a 97% cumulative diameter in a volume-based cumulative particle size distribution, D97 is 8.50 μm or less.

[0010] The above phosphor is a powder composed of phosphor fine particles whose D97 is equal to or less than a predetermined value, but the phosphor composition contains a relatively large amount of La, which suppresses light emission in the visible region and gives predominant light emission in the near-infrared region.

[0011] One aspect of the present disclosure also provides the following [2] to [3].

[0012] [2] The phosphor according to [1], wherein the value of (D90-D10) / D50 is 3.00 or less, where D10, D50, and D90 are the 10% cumulative diameter, 50% cumulative diameter, and 90% cumulative diameter in a volume-based cumulative particle size distribution. [3] An ink composition comprising the phosphor according to [1] or [2].

[0013] According to the present disclosure, it is possible to provide a near-infrared phosphor having a reduced sub-peak intensity. According to the present disclosure, it is also possible to provide an ink composition containing the above-described near-infrared phosphor.

[0014] FIG. 1 shows the fluorescence spectra of the phosphors prepared in the examples and comparative examples.

[0015] 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.

[0016] 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.

[0017] The phosphor according to one embodiment of the present disclosure has the general formula: (Eu(1-x)(1-y)La ｘ M （１－ｘ）ｚ ) ２ (Si （１－ｙ） Al ｙ ) ５ N ８ In the general formula, M represents Ba, or two or more elements consisting of Ba and one or more elements selected from the group consisting of Mg, Ca, and Sr. In the general formula, x represents a value of 0.05 or more and 0.20 or less, y represents a value of 0.00 or more and 0.10 or less, z represents a value of more than 0.44 and 0.80 or less, and (1-x)z is less than 0.70. When D97 is the 97% cumulative diameter in a volume-based cumulative particle size distribution, the phosphor has a D97 of 8.50 μm or less.

[0018] The phosphor is Eu ２ Si ５ N ８ In the phosphor represented by the composition formula above, some of the elements at the Eu site are substituted with La and M, and some of the elements at the Si site are substituted with Al.

[0019] In the above general formula, M contains at least Ba. From the viewpoint of further suppressing thermal degradation, the proportion of Ba among all elements corresponding to M may be, for example, 50 atomic % or more, 70 atomic % or more, or 90 atomic % or more. The elements corresponding to M may be substantially all Ba. In other words, the proportion of Ba among all elements corresponding to M may be 100 atomic %.

[0020] In the above general formula, the lower limit of the value of x may be, for example, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, or 0.10 or more. By setting the lower limit of the value of x within the above range, it is possible to introduce more local distortion into the crystal structure, which causes light emission that would normally occur in the visible range to be absorbed by the crystal having the distortion and extracted as near-infrared light (wavelength conversion). As a result, the emission intensity of the emission peak around 660 nm can be further reduced and the emission intensity of the near-infrared light can be further increased. In the above general formula, the upper limit of the value of x may be, for example, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, or 0.11 or less. By setting the upper limit of the value of x within the above range, the generation of heterophases caused by the presence of excess La can be further suppressed, and the emission of visible sub-peaks in the visible range can be suppressed, thereby further increasing the potential of the security ink in the visible range. When the particle diameter of the phosphor particles is large, it is not possible to grasp the influence of the value of x, that is, the fact that the above-mentioned effect can be obtained by adjusting the amount of La and balancing it with M, and it has been difficult to predict that such an effect would be obtained. In the above general formula, the value of x may be adjusted within the above-mentioned range, and may be, for example, 0.05 to 0.11, 0.06 to 0.18, 0.07 to 0.11, or 0.09 to 0.11.

[0021] In the above general formula, the lower limit of the value of y may be, for example, 0.01 or more, 0.02 or more, or 0.03 or more. In the above general formula, the upper limit of the value of y may be, for example, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, or 0.04 or less. In the above general formula, the value of y may be adjusted within the above range, and may be, for example, 0.01 to 0.09, or 0.03 to 0.08.

[0022] In the above general formula, the lower limit of the value of z may be, for example, 0.45 or more, 0.46 or more, 0.47 or more, 0.48 or more, 0.49 or more, or 0.50 or more. By having the lower limit of the value of z within the above range, the heat resistance of the phosphor can be improved and thermal degradation can be further suppressed. In the above general formula, the upper limit of the value of z may be, for example, 0.80 or less, 0.75 or less, 0.70 or less, 0.60 or less, or 0.55 or less. By preparing the phosphor so that the upper limit of z falls within the above range, the particle size of the phosphor can be further reduced. In the above general formula, the value of z may be adjusted within the above range, for example, 0.45 to 0.80, 0.45 to 0.75, 0.45 to 0.70, or 0.49 to 0.55.

[0023] In the above general formula, when M is Ba, the value of (1-x)z is less than 0.70, but may be adjusted as follows. In the above case, the upper limit of the value of (1-x)z may be, for example, 0.69 or less, 0.68 or less, 0.65 or less, 0.60 or less, or 0.50 or less. In the above case, the lower limit of the value of (1-x)z may be, for example, 0.40 or more, 0.43 or more, 0.44 or more, 0.45 or more, or 0.46 or more. In the above case, the value of (1-x)z may be adjusted within the above range, and may be, for example, 0.40 to 0.69, 0.43 to 0.60, or 0.44 to 0.50.

[0024] In the composition of the phosphor, the contents of europium (Eu), lanthanum (La), element M (Ba, Mg, Ca, and Sr), silicon (Si), and aluminum (Al) can be determined by quantitative analysis of the elements using an ICP optical emission spectrometer, and the amount of nitrogen (N) can be determined by subtracting the total value of the elements quantified by the ICP optical emission spectrometer from 100%. The presence of nitrogen atoms (N) can be confirmed using an oxygen / nitrogen analyzer. This measurement can determine the values ​​of x, y, and z in the general formula above. Examples of ICP optical emission spectrometers that can be used include a multi-type ICP optical emission spectrometer manufactured by Agilent Technologies (product name "Agilent 5110 VDV type") and the like. Examples of oxygen / nitrogen analyzers that can be used include a device manufactured by Horiba, Ltd. (product name "EMGA-920") and the like.

[0025] The crystal system of the phosphor particles constituting the phosphor according to the present disclosure may be an orthorhombic system, and the Eu ２ Si ５ N ８ It may have the same crystal system as the phosphor represented by the composition formula: Eu ２ Si ５ N ８ The lattice constants and axial angles of the phosphor represented by the composition formula are a = 0.57094(4) nm, b = 0.068207(4) nm, c = 0.93291(6) nm, and α = β = γ = 90.00°. ２ Si ５ N ８ The unit cell volume (product of a, b, and c) of the phosphor represented by the composition formula is 0.363 nm ３ The values ​​in parentheses above indicate the standard deviation, and are stated in accordance with the method defined by the International Union of Crystallography (IUCr).

[0026] The lattice constants a, b, and c and the unit lattice volume of the phosphor determined from the X-ray diffraction spectrum are, according to Vegard's law, ２ Si ５ N ８This is useful as an index for measuring the degree of substitution of La and M at the Eu site and the degree of substitution of Al at the Si site for a crystal represented by the composition formula.

[0027] The lattice constant a of the phosphor may be 0.574 to 0.577 nm, or 0.575 to 0.576 nm.

[0028] The lattice constant b of the phosphor may be 0.685 to 0.691 nm, or 0.686 to 0.688 nm.

[0029] The lattice constant c of the phosphor may be 0.935 to 0.941 nm, or 0.936 to 0.940 nm.

[0030] The unit cell volume of the phosphor is 0.368 to 0.374 nm ３ , 0.368-0.372nm ３ , 0.369-0.371 nm ３ It may be.

[0031] The 10% cumulative diameter (D10) in the volume-based cumulative particle size distribution of the phosphor may be 0.60 μm or less, 0.55 μm or less, 0.50 μm or less, 0.45 μm or less, or 0.43 μm or less. When the upper limit of D10 is within the above range, the phosphor can be uniformly dispersed with other components contained in the ink when mixed with the ink. The lower limit of the 10% cumulative diameter (D10) in the volume-based cumulative particle size distribution of the phosphor may be, for example, 0.15 μm or more, 0.20 μm or more, 0.25 μm or more, 0.30 μm or more, 0.35 μm or more, or 0.40 μm or more. When the lower limit of D10 is within the above range, the decrease in luminescence intensity due to particle size reduction can be minimized. The D10 may be adjusted within the above range, for example, 0.35 to 0.60 μm or 0.40 to 0.43 μm.

[0032] The 50% cumulative diameter (D50) in the volume-based cumulative particle size distribution of the phosphor may be, for example, less than 3.00 μm, 2.00 μm or less, 1.50 μm or less, 1.00 μm or less, or 0.95 or less. When the upper limit of the D50 is within the above range, the phosphor can be dispersed more uniformly even when other components are contained in the ink composition prepared by blending with a resin or the like. The lower limit of the 50% cumulative diameter (D50) in the volume-based cumulative particle size distribution of the phosphor may be, for example, 0.50 μm or more, 0.60 μm or more, 0.70 μm or more, 0.80 μm or more, or 0.85 μm or more. When the lower limit of the D50 is within the above range, the decrease in luminescence intensity associated with the reduction in particle size of the phosphor can be further suppressed. The D50 may be adjusted within the above range, for example, 0.50 to 1.50 μm, 0.70 to 1.00 μm, or 0.80 to 0.95 μm.

[0033] The upper limit of the 90% cumulative diameter (D90) in the volume-based cumulative particle size distribution of the phosphor may be, for example, 10.00 μm or less, 8.00 μm or less, 6.00 μm or less, 5.00 μm or less, or 4.00 μm or less, 3.00 μm or less, 2.90 μm or less, or 2.80 μm or less. When the upper limit of the D90 is within the above range, the potential of the phosphor in the printed portion can be further enhanced when an ink composition obtained by blending the phosphor with a resin or the like is printed. The lower limit of the 90% cumulative diameter (D90) in the volume-based cumulative particle size distribution of the phosphor may be, for example, 2.00 μm or more, 2.10 μm or more, 2.20 μm or more, 2.40 μm or more, 2.50 μm or more, 2.60 μm or more, or 2.65 μm or more. When the lower limit of the D90 is within the above range, the decrease in luminescence intensity due to particle size reduction can be further suppressed. The D90 may be adjusted within the above range, for example, 2.00 to 6.00 μm, 2.40 to 3.00 μm, or 2.65 to 2.80 μm.

[0034] The 97% cumulative diameter (D97) in the volume-based cumulative particle size distribution of the phosphor is 8.50 μm or less, but may be, for example, 8.50 μm or less, 8.00 μm or less, 7.00 μm or less, 6.00 μm or less, 5.00 μm or less, or 4.90 μm or less. The phosphor according to the present disclosure has a relatively high amount of La, and even if D97 falls within the above range, the occurrence of sub-peaks is suppressed. The lower limit of the 97% cumulative diameter (D97) in the volume-based cumulative particle size distribution of the phosphor may be, for example, 3.40 μm or more, 3.60 μm or more, 3.80 μm or more, 4.00 μm or more, or 4.20 μm or more. By having the lower limit of the D97 within the above range, an increase in the viscosity of the ink composition can be further suppressed when blended with a resin or the like to prepare an ink composition. The D97 may be adjusted within the above range, for example, 4.00 to 8.50 μm, 4.00 to 5.00 μm, or 4.20 to 4.90 μm.

[0035] When the 10% cumulative diameter, 50% cumulative diameter, and 90% cumulative diameter in the volume-based cumulative particle size distribution of the phosphor are defined as D10, D50, and D90, respectively, the value of (D90-D10) / D50 (span value) may be, for example, 3.00 or less, 2.90 or less, 2.80 or less, 2.70 or less, 2.60 or less, 2.55 or less, 2.50 or less, or 2.48 or less. The span value may be, for example, 2.10 or more, 2.20 or more, 2.30 or more, 2.35 or more, 2.40 or more, or 2.45 or more. The span value may be adjusted within the above-mentioned range, for example, 2.10 to 3.00, 2.40 to 2.90, 2.40 to 2.80, or 2.45 to 2.55.

[0036] In this specification, the 10% cumulative diameter (D10), 50% cumulative diameter (D50), 90% cumulative diameter (D90), and 97% cumulative diameter (D97) in the volume-based cumulative particle size distribution of the phosphor are measured in accordance with the particle size distribution measurement method using laser diffraction and scattering described in JIS R 1629:1997 "Method for measuring particle size distribution by laser diffraction and scattering of fine ceramic raw materials." They refer to the particle diameters at which the integrated values ​​from the smallest particle size in the volume-based particle size distribution curve reach 10%, 50%, 90%, and 97%, respectively, of the total. D10, D50, D90, and D97 can be specifically measured and determined using the procedures described in the Examples section of this specification. D50 is also called the median diameter and refers to the average particle size of the target particles. D10, D50, D90, and D97 can be controlled by adjusting conditions such as the amounts of Ba source and La source mixed, heating temperature, and heating time when producing the phosphor.

[0037] The phosphor according to the present disclosure has an emission peak with maximum emission intensity in the wavelength range of 820 to 860 nm in the fluorescence spectrum obtained when irradiated with light having a wavelength of 450 nm. The phosphor also has no emission peak in the wavelength range of less than 800 nm, or if it does have an emission peak, the emission intensity is suppressed to a low level. In particular, the emission intensity of the emission peak around 660 nm is suppressed.

[0038] In the fluorescence spectrum obtained when the phosphor is irradiated with light having a wavelength of 450 nm, the value of the emission intensity at a wavelength of 660 nm relative to the emission intensity at a wavelength of 840 nm ([emission intensity at a wavelength of 660 nm] / [emission intensity at a wavelength of 840 nm]) is suppressed to a small value. The upper limit of the value of [emission intensity at a wavelength of 660 nm] / [emission intensity at a wavelength of 840 nm] can be, for example, 0.220 or less, 0.200 or less, 0.150 or less, 0.100 or less, 0.090 or less, 0.080 or less, 0.075 or less, 0.070 or less, 0.068 or less, 0.060 or less, 0.055 or less, or 0.050 or less.

[0039] The above-mentioned phosphor has an emission peak in the near-infrared region and the emission intensity of a sub-peak in the visible light region is suppressed or the sub-peak is absent, making it useful as a phosphor for security ink. An ink composition according to an embodiment of the present disclosure is an ink composition containing the above-mentioned phosphor. The ink composition may be a security ink.

[0040] An example of a method for producing the above-mentioned phosphor includes firing a raw material mixture containing a Eu source, a La source, a M source, a Si source, and an Al source at 1300°C or higher in an inert gas atmosphere to obtain a fired product (hereinafter also referred to as the firing step), and pulverizing and classifying the fired product to obtain a powder having a 97% cumulative diameter (D97) in a volume-based cumulative particle size distribution of 8.50 μm or less (hereinafter also referred to as the pulverizing and classifying step).

[0041] In the raw material mixture, at least one selected from the group consisting of an Eu source, a La source, an M source, a Si source, and an Al source is a nitride. For example, the raw material mixture contains at least one of europium nitride, lanthanum nitride, barium nitride, magnesium nitride, calcium nitride, strontium nitride, silicon nitride, and aluminum nitride.

[0042] The blending amount of each component in the raw material mixture can be adjusted according to the target composition of the phosphor. The blending amount of the La source in the raw material mixture may be 4 mol% or more, 5 mol% or more, 6 mol% or more, or 7 mol% or more, based on the total amount of the raw material mixture. By adjusting the blending amount of the La source to be within the above range, a near-infrared phosphor with suppressed emission in the visible region can be more easily prepared. The blending amount of the La source in the raw material mixture may be 10 mol% or less, 9 mol% or less, or 8 mol% or less, based on the total amount of the raw material mixture. By adjusting the blending amount of the La source to be within the above range, the intensity of near-infrared emission can be further increased.

[0043] The inert gas atmosphere in the firing step may be, for example, a nitrogen gas atmosphere. The atmosphere in the firing step may be set under pressurized conditions, for example, 0.5 MPa·G or more, 0.7 MPa·G or more. By firing under pressurized conditions, decomposition of the fired product can be more sufficiently suppressed. The pressure of the atmosphere in the firing step may be, for example, 1.0 MPa·G or less, or 0.9 MPa·G or less.

[0044] The firing temperature in the firing step is set to 1300°C or higher to adjust the chemical composition within the phosphor particles to be uniform, and the relatively low firing temperature suppresses excessive particle growth. The firing temperature in the firing step may be, for example, 1300°C or higher, 1350°C or higher, 1400°C or higher, or 1450°C or higher. The upper limit of the firing temperature in the firing step may be, for example, 1900°C or lower, 1800°C or lower, 1700°C or lower, or 1600°C or lower. By setting the upper limit of the firing temperature within the above range, it is possible to further suppress the particle size from becoming too large for blending with ink due to growth of the phosphor particles.

[0045] The firing time in the firing step may be, for example, 1 to 96 hours, 1 to 80 hours, 1 to 60 hours, 1 to 30 hours, 2 to 10 hours, 3 to 10 hours, or 3 to 5 hours.

[0046] The fired product can be pulverized in the pulverizing and classifying step using, for example, a jet mill, a stamp mill, a vibration mill, a ball mill, or the like.

[0047] After the pulverization in the pulverization and classification step, classification is carried out. This classification may be so-called elutriation classification.

[0048] 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.

[0049] 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.

[0050] Example 1: 11.318 g of lanthanum nitride (LaN, manufactured by Kojundo Chemical Laboratory Co., Ltd.), 55.282 g of europium nitride (EuN, manufactured by Taiheiyo Cement Corporation), and 55.282 g of barium nitride (Ba ３ N ２ , manufactured by Materion Co., Ltd.) was 48.852 g, silicon nitride (Si ３ N ４ 83.068 g of aluminum nitride (AlN, E-10 grade, manufactured by UBE Corporation) and 3.034 g of aluminum nitride (AlN, E grade, manufactured by Tokuyama Corporation) were weighed out and mixed in a mortar under a nitrogen atmosphere for 10 minutes to obtain a raw material mixture.

[0051] Next, the obtained raw material mixture was placed in a boron nitride container and heated to 1500°C at a heating rate of 10°C / min in a nitrogen gas atmosphere at a pressure of 0.8 MPa G. By holding at 1500°C for 8 hours, a sintered block was obtained.

[0052] The fired product was crushed in an alumina mortar to obtain a crushed product. The crushed product was passed through a nylon sieve with an opening of 45 μm (330 mesh). The fraction that passed through the sieve was pulverized in a ball mill for 2 hours to obtain a phosphor.

[0053] <Composition Analysis of Phosphor> The composition of the obtained phosphor was analyzed. Specifically, 10 mg of the obtained phosphor was placed in a platinum crucible, 2 g of alkaline flux was added, and the phosphor was melted in an electric furnace. After cooling, 10 mL of hydrochloric acid was added to the platinum crucible and heated in a warm bath to melt the phosphor. The resulting solution was adjusted to a constant volume of 100 mL. This 100 mL solution was diluted 10 times with pure water to prepare a sample solution. The composition of the constituent elements of the phosphor was analyzed using a multi-type IPC optical emission spectrometer (Agilent Technologies, product name "Agilent 5110 VDV type"). Based on the obtained analysis results, the values ​​of x, y, and z in general formula (1) were determined. Nitrogen was confirmed using an oxygen / nitrogen analyzer "EMGA-920" (product name) manufactured by Horiba, Ltd., and the total value of the elements detected by the IPC emission spectroscopic analysis was subtracted from 100% to determine the proportion of nitrogen. The results are shown in Table 1.

[0054] <Particle size distribution of phosphor> The particle size distribution of the obtained phosphor was measured in accordance with the particle size distribution measurement method by laser diffraction / scattering described in JIS R 1629:1997 "Method for measuring particle size distribution of fine ceramic raw materials by laser diffraction / scattering method." Specifically, 0.03 g of the phosphor to be measured was first added to 100 mL of ion-exchanged water containing 0.05 mass% sodium hexametaphosphate, and the mixture was dispersed for 3 minutes using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., product name "Ultrasonic Homogenizer US-150E", amplitude: 100%, oscillation frequency: 19.5 kHz, tip size: φ20, amplitude: 32±2 μm) to prepare a measurement sample. Thereafter, the particle size was measured using a particle size distribution measuring device (manufactured by Microtrac Bell Corporation, product name "Microtrac MT3300EX II"). From the obtained particle size distribution, D10, D50, D90, and D97 were determined. Furthermore, based on the determined D10, D50, and D90 values, (D90-D10) / D50 (span value) was calculated.

[0055] <Determination of Lattice Constant and Lattice Volume> X-ray diffraction measurement was performed on the powder prepared in Example 1 using an X-ray diffractometer (manufactured by Rigaku Corporation, product name: Ultima IV) to measure the lattice constants a, b, and c of the phosphor powder. The unit lattice volume was determined from the obtained values ​​of the lattice constants a, b, and c. The measurement range was 10 to 60°. The results are shown in Table 1.

[0056] <Evaluation of Phosphor: Emission Spectrum> The emission spectrum of the obtained phosphor was obtained. Specifically, the phosphor to be measured was first filled into a concave cell so that the surface was smooth, and the cell was attached to the opening of an integrating sphere. Monochromatic light, separated into wavelengths of 450 nm from a Xe lamp (light source), was introduced into the integrating sphere using an optical fiber as excitation light. This excitation light was irradiated onto the phosphor powder to be measured, and the fluorescence spectrum was measured. A spectrofluorometer (manufactured by Horiba, Ltd., product name "Fluorolog-3-iHR-NIR") was used for the measurement. The wavelength showing the highest intensity in the wavelength range from 500 nm to 1400 nm in the obtained fluorescence spectrum data was determined as the emission peak wavelength. Furthermore, the emission intensity at a wavelength of 840 nm and the emission intensity at a wavelength of 660 nm were determined for the obtained fluorescence spectrum, and the value of [emission intensity at a wavelength of 660 nm] / [emission intensity at a wavelength of 840 nm] was calculated. For reference, the fluorescence spectra of the phosphors prepared in the examples and comparative examples are shown in FIG.

[0057] Example 2 A phosphor was obtained in the same manner as in Example 1, except that the grinding time in the ball mill was changed to 4 hours. The obtained phosphor was evaluated in the same manner as in Example 1.

[0058] Example 3 A phosphor was obtained in the same manner as in Example 1, except that the time for pulverization using a ball mill was changed to 8 hours. The obtained phosphor was evaluated in the same manner as in Example 1.

[0059] Example 4 A phosphor was obtained in the same manner as in Example 1, except that the time for pulverization using a ball mill was changed to 16 hours. The obtained phosphor was evaluated in the same manner as in Example 1.

[0060] (Example 5) A phosphor was obtained in the same manner as in Example 1, except that the values ​​of x, y, and z in the target composition were changed as shown in Table 1 and the time for pulverization using a ball mill was changed to 16 hours. The obtained phosphor was evaluated in the same manner as in Example 1.

[0061] Example 6 A phosphor was obtained in the same manner as in Example 1, except that the values ​​of x, y, and z in the target composition were changed as shown in Table 1 and the time for pulverization using a ball mill was changed to 16 hours. The obtained phosphor was evaluated in the same manner as in Example 1.

[0062] Example 7 A phosphor was obtained in the same manner as in Example 1, except that the values ​​of x, y, and z in the target composition were changed as shown in Table 1 and the time for pulverization using a ball mill was changed to 16 hours. The obtained phosphor was evaluated in the same manner as in Example 1.

[0063] (Comparative Example 1) A phosphor was obtained in the same manner as in Example 1, except that the values ​​of x, y, and z in the target composition were changed as shown in Table 2, the firing temperature was changed to 1600°C, and the fired product was not subjected to crushing treatment. The obtained phosphor was evaluated in the same manner as in Example 1.

[0064] Comparative Example 2 A phosphor was obtained in the same manner as in Example 4, except that the values ​​of x, y, and z in the target composition were changed as shown in Table 2. The obtained phosphor was evaluated in the same manner as in Example 1.

[0065] (Comparative Example 3) A phosphor was obtained in the same manner as in Example 1, except that the values ​​of x, y, and z in the target composition were changed as shown in Table 2, the firing temperature was changed to 1600°C, and the fired product was not subjected to crushing treatment. The obtained phosphor was evaluated in the same manner as in Example 1.

[0066]

[0067]

[0068] According to the present disclosure, it is possible to provide a near-infrared phosphor having a reduced peak intensity of a sub-peak in the visible region. According to the present disclosure, it is also possible to provide an ink composition containing the above-described near-infrared phosphor.

Claims

1. General formula: (Eu(1-x)(1-y)La ｘ M （１－ｘ）ｚ ) ２ (Si （１－ｙ） Al ｙ ) ５ N ８ A phosphor represented by the formula: wherein, in said general formula, M represents Ba, or two or more elements of Ba and one or more elements selected from the group consisting of Mg, Ca, and Sr, x represents a numerical value of 0.05 or more and 0.20 or less, y represents a numerical value of 0.00 or more and 0.10 or less, z represents a numerical value of more than 0.44 and 0.80 or less, and (1-x)z is less than 0.70, and when D97 is defined as a 97% cumulative diameter in a volume-based cumulative particle size distribution, D97 is 8.50 μm or less.

2. The phosphor according to claim 1, wherein the value of (D90-D10) / D50 is 3.00 or less, where D10, D50, and D90 are the 10% cumulative diameter, 50% cumulative diameter, and 90% cumulative diameter in the volume-based cumulative particle size distribution, respectively.

3. An ink composition comprising the phosphor according to claim 1 or 2.

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